This page explains the assumptions behind the estimates and calculators shown on realatrends.com, including the monthly payment estimate on listing pages. Every figure they produce is an estimate for information only. None of it is a loan offer, a commitment to lend, a quote, or advice for your situation. Verify any number that matters to your decision with your lender, the county assessor, the HOA, and your own advisors.
The monthly payment estimate
Listing pages show an estimated monthly payment at 10, 20, and 30 percent down, plus an all-cash carrying cost. The home price defaults to the listing price and can be adjusted, down to half the listing price with the slider or to any amount by typing. Every figure recomputes from the price you set, so an edited estimate reflects your hypothetical offer, not the listing price.
Principal and interest assume a 30-year fixed loan at the Freddie Mac Primary Mortgage Market Survey national average, updated weekly. That survey reflects conforming loans to strong-credit borrowers, and it is not a rate offered to you by Realatrends Real Estate or anyone else. Your actual rate depends on credit, down payment, loan program, and lender. Loans above the conforming limit are jumbo loans: jumbo rates, down-payment minimums, and qualifying standards differ from the survey average, and low-down-payment structures at jumbo size may carry costs the estimate does not show.
Below 20 percent down, the estimate adds a mortgage insurance line modelled at 0.5 percent of the loan per year. Actual mortgage insurance pricing varies by lender and program, and some lenders price it into the rate instead.
Property taxes
The MLS feed does not carry tax data, so the tax line is modelled from a typical effective rate for each city, ranging from roughly 1 percent in the lower-tax inland cities to about 1.6 percent in communities with heavy Mello-Roos. For cities where community facilities district taxes are common, such as Ladera Ranch and Rancho Mission Viejo, the modelled rate already includes a typical Mello-Roos allowance. For other listed cities it excludes Mello-Roos and special assessments. For a city we do not track, the estimate uses a typical Orange County rate. Actual assessments vary parcel by parcel: two homes on the same street can owe different special taxes, and a district can expire during your ownership. Our Mello-Roos and HOAs guide explains how these districts work.
The tax line assumes reassessment at the price shown, per Proposition 13. The seller’s current bill may be far lower than the modelled figure because long-held homes carry older assessed values, and a supplemental bill usually follows a sale. Request the estimated total tax rate for any specific address during escrow.
Home insurance
The insurance line is modelled at roughly 0.35 percent of the price per year, and it is the least certain input in the estimate. Real premiums are priced on rebuild cost rather than purchase price, and in coastal Orange County the land is often a large share of the price. Wildfire exposure, brush zones, and carrier availability move premiums by a wide multiple here, and homes written through the California FAIR Plan can cost several times the modelled figure. Get a real quote before you budget.
HOA dues
When the listing feed reports HOA dues, the estimate includes them as reported. Dues change, and some communities carry more than one association, so confirm current amounts with the HOA. When the feed reports no dues, the estimate shows the HOA line as not reported and includes nothing for it, which does not mean the property has no dues.
What the estimate excludes
The estimated total excludes closing costs, flood and earthquake coverage, utilities, maintenance, any HOA dues not reported in the listing data, and any special assessments beyond the modelled tax rate. On co-op or leasehold properties, fee structures can differ from anything modelled here.
Market data
Market figures on city pages, market reports, and embedded widgets come from published Redfin, Realtor.com, and Zillow data at the ZIP code level, refreshed on their publication schedules. ZIP-level data cannot distinguish communities that share a ZIP code, and medians in markets with few sales can move sharply on a handful of closings. Sold data shown on this site is a sampling of our archive, not a complete record.
Questions
If a figure on this site looks wrong, or you want the assumptions behind a specific number, call Realatrends Real Estate at (949) 494-8830 or use the contact page. We would rather correct a number than have you rely on a bad one.
Orange County property tax data
The property tax figures published on our Orange County property tax page are estimates, and they model a buyer purchasing at a city median price rather than what current owners pay. California reassesses a property at its purchase price under Proposition 13, so a long-held home is assessed well below market value and carries a considerably smaller bill than the same home would for a new buyer.
Effective tax rates are median figures from the Ownwell Orange County dataset, vintage April 2026. Median home prices come from our own market data. Every rate is a citywide median, so an individual property, particularly one in a community carrying a Mello-Roos levy, will differ from the modeled figure. The Orange County Assessor and the Treasurer-Tax Collector are the authorities on any specific parcel.