Buyer-side work

The true monthly cost worksheet

The all-in monthly number for a specific home, including the reassessed property tax the portals get wrong, before your buyer falls in love with the wrong budget.

The idea

What this does

Portals show the seller's tax bill, and in California that number can be a quarter of what your buyer will actually pay after reassessment. Add realistic insurance, HOA dues, utilities, and a maintenance reserve for a home of that age, and the "monthly payment" conversation changes. This prompt walks the AI through building the honest worksheet, shows every assumption, and explains the difference from the portal number in plain words your client will understand.

Gather these first

Before you start

Listing details: price, HOA dues if any, home age and size, and anything you know about systems (roof year, pool, AC)
Your buyer's loan sketch: down payment percent and quoted rate, even roughly
Two minutes to answer the questions the AI asks back

Step by step

How to use it

Start a new chat, copy the prompt, fill in what you know, and paste.
The AI will ask for anything essential that is missing. Answer briefly; estimates are fine if you label them.
Sanity-check the two inputs that move the number most: the property tax rate and the insurance estimate.
Ask for a client-friendly summary at the end and forward it.

Copy everything in the box

The prompt

Paste this into your AI tool Fill anything in [BRACKETS] with your details

You are a careful financial calculator and explainer for me, a residential real-estate agent. Build a true monthly cost estimate for my buyer for [PROPERTY ADDRESS or DESCRIPTION]. What I know so far: - Purchase price under consideration: [PRICE] - Down payment and rate: [e.g. 20% down, quoted 6.4% on a 30-year fixed] - Property details: [YEAR BUILT, SQFT, HOA DUES if any, POOL yes/no, ROOF/HVAC AGE if known] - Location: [CITY, STATE] Step 1: ask me for any missing input that materially changes the result (tax rate details, Mello-Roos or special assessments, insurance quotes if we have one). Ask only what you need, in one batch, then proceed with labeled assumptions for whatever I cannot provide. Step 2: produce the worksheet. 1. PRINCIPAL AND INTEREST. 2. PROPERTY TAX, done properly: base it on the PURCHASE price with this location's actual rate, note supplemental or special assessments, and if this is California, explain the reassessment and the first-year supplemental bill in one short paragraph. 3. INSURANCE, as a RANGE, with a note if location or roof age suggests quotes should be gathered early. 4. HOA, utilities by season, and a maintenance reserve appropriate to the home's age and systems (state the rule of thumb you used). 5. THE TOTALS. All-in monthly for year one and year three, side by side with the naive portal-style estimate, with a line-by-line explanation of every difference. 6. WHAT WOULD CHANGE IT. The three assumptions most worth verifying, and who to ask. Rules: show every assumption and label it as such. Ranges over false precision. No investment or tax advice; where taxes get personal, say "confirm with your CPA." Keep the final summary short enough to forward to a client.

→Anything in [BRACKETS] is yours to fill in. Delete a bracket line if it does not apply; the prompt still works.

The result

What you'll get back

A year-one and year-three all-in monthly figure with every assumption visible
The portal-versus-reality explanation, ready to hand to a client
The reassessment story told correctly, which buyers rarely hear before escrow
A short list of what to verify and with whom

Level it up

Make it yours

Run it twice at two price points and ask for the comparison.
Follow up with "what monthly income does the standard lender math imply for this payment" when a budget conversation is coming.
For a high-fire-risk or flood area, pair this with playbook 09 before anyone gets attached.

Keep it honest

The output is a decision aid built on stated assumptions, not a lender quote or tax advice; the CPA and lender lines are there for a reason.
Verify special assessments and Mello-Roos directly with the county; a wrong district lookup is the most common miss.
If the insurance range looks wide, that is the tool being honest; get a real quote early instead of narrowing it by hope.