ARV without the optimism tax
Comp like the appraiser who will eventually judge your flip — the five filters, the median-of-three discipline, and the habit that catches a $15k error before it becomes your $15k.
Every number in your deal flows from one estimate: what the finished house sells for. Get ARV right and the MAO protects you automatically; get it $15k high and — through the 70% rule — you just overpaid by $10.5k with borrowed money. This lesson installs the appraiser's discipline, because an actual appraiser will re-run your work at the exit, and their number is the one that counts.
The five filters, non-negotiable
Real comps pass all five. Every filter you bend "just this once" is the optimism tax compounding:
- Sold, not listed. Closed sales are evidence; listings are hopes with photography. (Actives matter as your future competition — three renovated actives sitting unsold at your ARV is the market voting no.)
- Same micro-market. Half a mile max — and never across a school line, highway, railroad, or the street locals name with a face. Drive every comp; boundaries the map can't see move values 10–20%.
- Sold within 90–180 days. Last summer's sale is a different market's opinion.
- Same kind. Within ~20% of square footage, same story count, same vintage band. Appraisers won't cross those lines; you can't either.
- Renovated to YOUR finish level. You're valuing your finished product — the mid-grade rehab does not comp against the designer flip with the $9k range.
The median discipline
Three qualifying comps at $285k, $292k, $318k → your ARV lives near $290k. The $318k sale is a research question (corner lot? bidding war? 400 extra feet?) — never a foundation. Comping to the outlier is the single most expensive habit in this business, and it always feels justified in the moment, which is exactly why the rule is procedural: median of the best three, every time. Adjust for concrete differences in dollars (garage ±$8–15k, bath ±$5–12k), bracket the subject with comps above and below, and cap total adjustments at ~10–15% — need more, and the comp doesn't qualify. → The complete method
The two-sided error
Under-comping costs you too — the deal you walked from at a too-conservative $270k ARV was someone else's honest $290k and their $14k of margin. The discipline isn't pessimism; it's accuracy: your growing file of actual sale prices versus your pre-purchase ARVs is the most valuable spreadsheet you'll ever keep. Professionals track it and converge within ±5% inside a year. That file — not confidence — is what lets you one day bid faster than competitors who still need a weekend to comp.
Where the data lives
MLS sold data is the gold standard — via an investor-friendly agent, or your own license (which also pays you 2.5–3% on every personal buy). Portals' sold filters work with county-record verification; automated estimates never do (they price the current dented condition and know nothing of your renovation). And walk open houses of renovated inventory monthly — comping is pattern recognition, and the patterns live in finished rooms.
The pitfall to skip: accepting the wholesaler's ARV. It's a sales document. Re-comp every deal you're sent — the good wholesalers expect it, and the bad ones are counting on you not to.
Do this now: Comp three renovated houses that sold in your farm area last quarter before looking at their prices, then check yourself. Off by more than 5%? Find which filter you bent. That exercise, weekly, builds the appraiser's eye in about six weeks.