If you're using ChatGPT or Google Gemini the same way you were a year ago (open a new chat, type a question, get a generic answer), you're leaving most of the value on the table. The real power of these platforms is in customization.
OpenAI calls them Custom GPTs. Google calls them Gems. The concept is the same: you build a specialized AI assistant with pre-loaded instructions, knowledge files, and a defined personality so it gives you exactly the kind of answers you need, every time, without re-explaining your context.
This isn't a gimmick. Guild Mortgage built an internal Custom GPT system that now handles routine loan processing tasks company-wide. FinLocker offers a full AI toolkit with over a dozen mortgage-specific GPTs (Fannie Mae wizard, FHA wizard, underwriting assistant). And plenty of individual LOs are quietly building their own.
What Are Custom GPTs and Gemini Gems?
ChatGPT Custom GPTs
- Available on ChatGPT Plus, Team, and Enterprise plans
- Custom instructions, knowledge files (PDFs, docs, spreadsheets), and enabled tools (code, browsing, image gen)
- Shareable via link (team, company, or public)
- Can connect to external APIs via "Actions"
Google Gemini Gems
- Available on Gemini Advanced (Google One AI Premium)
- Custom persona, tone, style, and detailed instruction blocks
- Deep integration with Google Workspace (Docs, Sheets, Gmail)
- Best if you're already in the Google ecosystem
Which should you pick? If you live in Microsoft Office and Outlook, lean toward Custom GPTs (they pair well with Copilot). If you're a Google Workspace user, Gems integrate more naturally. You can use both, though. Many LOs keep 2-3 GPTs for work and 1-2 Gems for personal stuff, or vice versa.
4 Work GPTs/Gems Every Loan Officer Should Build
1. Pre-Approval Communicator
Custom GPTDrafts personalized pre-approval letters, conditional approval explanations, and denial follow-ups in your voice.
Sample Instructions (paste into the builder)
"You are a senior mortgage loan officer with 15 years of experience. You write client-facing emails and letters that are warm, professional, and jargon-free. You always explain the 'why' behind decisions. You follow ECOA/TILA compliance. You sign off as [Your Name], [Your NMLS#]."
Knowledge Files to Upload
- Your email signature and bio
- Company letterhead template
- FNMA/FHA/VA guideline cheat sheet
- Your top 10 most-sent email templates
2. Loan Scenario Calculator
Custom GPTRuns quick rate comparisons, monthly payment estimates, and DTI calculations on the fly during client calls.
Sample Instructions (paste into the builder)
"You are a mortgage math assistant. When given a loan amount, rate, and term, you calculate the monthly P&I payment, total interest paid, and APR estimate. You can compare up to 3 scenarios side by side. You always show your math. You flag if a DTI ratio exceeds 43% or 50%."
Knowledge Files to Upload
- Current rate sheet (upload weekly)
- FHA/VA funding fee schedules
- County loan limit tables
- MI rate cards
3. Social Media Ghostwriter
Gemini GemCreates on-brand social posts for rate updates, closed loan celebrations, market commentary, and educational content.
Sample Instructions (paste into the builder)
"You write social media posts for a mortgage loan officer. Tone: friendly, knowledgeable, never salesy. You write for LinkedIn, Facebook, and Instagram. Each post includes a hook, 2-3 sentences of value, and a soft CTA. You never make rate guarantees or income claims. You match the voice in the example posts I've uploaded."
Knowledge Files to Upload
- 20 of your best-performing past posts
- Brand voice guide or style notes
- Compliance do's and don'ts for mortgage social
- Local market stats PDF
4. Compliance Quick-Check
Custom GPTReviews your draft emails, social posts, and marketing materials for RESPA, TILA, ECOA, and TCPA red flags before you send.
Sample Instructions (paste into the builder)
"You are a mortgage compliance reviewer. When I paste draft content, you scan it for potential violations of RESPA, TILA, ECOA, TCPA, and state-specific advertising rules. You flag issues with a severity rating (high/medium/low) and suggest compliant alternatives. You are not a lawyer and always recommend final legal review for anything rated high."
Knowledge Files to Upload
- CFPB advertising guidance PDF
- State-specific marketing rules for your state(s)
- Company compliance manual excerpts
3 Personal GPTs/Gems for Life Outside the Office
Once you see how well a focused AI assistant works for loan origination, you'll want them everywhere. Here are three personal GPTs that top-producing LOs are quietly using to reclaim time at home.
1. Meal Planner
Gemini GemPlans weekly dinners around dietary restrictions, what's already in the fridge, and a grocery budget.
Sample Instructions
"You are a home meal planning assistant. You know my family's dietary preferences (uploaded). You suggest 5 weeknight dinners each Sunday, generate a combined grocery list organized by store section, and estimate total cost. You prioritize meals under 30 minutes on weeknights. You remember what we liked from past weeks."
Why this one? Busy LOs don't stop being busy at 5pm. Reclaiming the 'what's for dinner' decision saves real mental energy.
2. Home Renovation Planner
Custom GPTTracks a remodel project with budget, contractor questions, permit research, and material comparisons.
Sample Instructions
"You are a home renovation project manager. You help me track budgets, timelines, and contractor bids for my [bathroom/kitchen/etc.] remodel. You compare material options with pros/cons and price ranges. You generate a list of questions to ask contractors. You flag if costs exceed my stated budget."
Why this one? You already know mortgages. Apply that same structured thinking to your own property with an AI that remembers the whole project.
3. Kids Homework Helper
Gemini GemExplains math, science, and reading concepts at your kid's grade level without doing the work for them.
Sample Instructions
"You are a patient tutor for a [grade level] student. You never give direct answers. You ask guiding questions, break problems into smaller steps, and celebrate when the student gets it right. You explain concepts using real-world examples. You match the curriculum standards for [state]."
Why this one? The Socratic method is hard to pull off at 8pm after a 12-hour day. Let AI do the patient teaching while you sit next to them.
Step-by-Step: Building Your First Custom GPT or Gem
ChatGPT Custom GPT
- 1Go to chatgpt.com/gpts/editor or click Explore GPTs in the sidebar, then Create.
- 2Give it a name that tells you what it does at a glance (e.g., 'Pre-Approval Email Writer').
- 3Write detailed instructions in the Configure tab. Paste in the sample instructions above and customize them.
- 4Upload 3-5 focused knowledge files. Less is more. Specific beats comprehensive.
- 5Enable the tools it needs: Code Interpreter for calculations, Web Browsing for rate research, DALL-E for image generation (usually off for work bots).
- 6Set sharing to 'Only me' to start. You can open it to your team later.
- 7Run 10 test prompts. Refine instructions based on what comes back wrong.
Google Gemini Gem
- 1Open the Gemini app (gemini.google.com) and click the + button or 'Create Gem.'
- 2Name it and write a short persona description (e.g., 'Mortgage social media writer').
- 3Add detailed instruction blocks: persona, tone, output format, constraints, and compliance notes.
- 4Upload reference files or link Google Docs/Sheets that contain your knowledge base.
- 5If you use Google Workspace, enable the integrations so it can pull from your Drive, Gmail, or Calendar.
- 6Test with varied prompts to check for consistency and accuracy.
- 7Refine. Gems improve dramatically after 2-3 rounds of instruction tuning.
The Real Secret: Writing Good Instructions
The instructions you write are 80% of what makes a Custom GPT or Gem useful or useless. Here's a formula that works:
"You are a mortgage loan officer with 10 years of experience specializing in first-time homebuyers."
Gives the AI a perspective and expertise level.
"You are writing for borrowers who have never bought a home. Avoid jargon. If you must use a term like DTI or LTV, explain it in parentheses."
Controls the reading level and tone.
"Always respond with a subject line, email body (under 150 words), and a P.S. line with a soft call to action."
Gives you consistent, usable output every time.
"Never guarantee rates. Never make income claims. Never reference competitors by name. Always include NMLS# in signatures."
Keeps you out of compliance trouble.
"Refer to the uploaded rate sheet for current pricing. If you don't have current data, say so and suggest I check with my pricing desk."
Tells it when to use files vs. general knowledge.
Copy-paste tip: Start with the sample instructions from the examples above, then swap in your own details. You don't need to write instructions from scratch. Iterate. After a week of use, you'll know exactly what to add or remove.
5 Pitfalls That Waste Everyone's Time
Pitfall #1: Instructions that are too vague
You are a helpful assistant for mortgage stuff.
You are a senior mortgage loan officer who writes client emails. Tone is warm and professional. You always explain the 'why' behind decisions. You follow ECOA compliance. You sign off with my name and NMLS#.
The more specific your instructions, the less you have to correct the output. Think of it like training a new assistant on their first day: spell it out.
Pitfall #2: Uploading too much (or too little) knowledge
Uploading your entire 200-page company operations manual.
Uploading the 5 specific pages that cover the topic this GPT handles.
Custom GPTs search uploaded files, but they're not great at finding needles in haystacks. Smaller, focused files get better results than massive document dumps.
Pitfall #3: Forgetting to update knowledge files
Rate sheet from 3 months ago still attached to your Loan Scenario Calculator.
Calendar reminder every Monday: swap in this week's rate sheet.
Your Custom GPT is only as current as the files you give it. Stale data means wrong answers, and wrong answers erode trust fast.
Pitfall #4: Making one GPT do everything
One GPT that writes emails, calculates payments, reviews compliance, and posts to social media.
Separate GPTs for each job, each with focused instructions and relevant files.
The more roles you pile onto one GPT, the worse it gets at all of them. Focused assistants outperform jack-of-all-trades bots every time.
Pitfall #5: Never testing before trusting
Building a GPT and immediately using the output in a client email.
Running 10 test prompts across different scenarios, checking the output, and refining instructions before going live.
Treat the first week as a trial run. Copy the outputs into a doc, read them critically, and tweak the instructions based on what's off. This is where most people give up too early.
How to Get the Most Out of Your Custom Assistants
Review and refine monthly
Set a calendar reminder to re-read your GPT's instructions once a month. Your workflow evolves. Your GPT should too.
Share with your team
If you're in a branch, share your best GPTs with other LOs. They'll improve them with their own edge cases.
Stack them together
Use your Compliance Quick-Check GPT to review the output from your Social Media Ghostwriter. Two GPTs are better than one.
Pin your favorites
Both ChatGPT and Gemini let you pin GPTs/Gems to your sidebar. Pin your top 3 so they're one click away, not buried in a list.
Use conversation starters
Both platforms let you set suggested prompts. Add 4-5 that match your most common use cases so you can start fast.
Build before you need it
Don't wait until you're slammed to build a GPT. Spend a quiet Friday afternoon setting up 2-3. Future-you will be grateful.
The Bottom Line
A Custom GPT or Gemini Gem takes about 15 minutes to set up. After that, it saves you 15 minutes (or more) every single day. The math is simple.
Start with one. The Pre-Approval Communicator or the Social Media Ghostwriter are the two that most LOs get value from fastest. Use it for a week. Refine the instructions based on what comes back. Then build a second one.
Before you know it, you'll have a small team of AI assistants that know your voice, your compliance requirements, your market, and your preferences. That's not a gimmick. That's a genuine competitive advantage.