From the threads here, overruns rarely come from one big surprise. They come from a lot of small ones nobody wrote down. Here's a simple structure that seems to catch them early:

1. Break the budget into trade categories (demo, framing, electrical, plumbing, HVAC, roof, windows, drywall, paint, flooring, kitchen, baths, exterior, landscaping, permits/fees). Add a contingency line of its own that you only touch after writing down why.

2. Three columns per line: Budget / Committed / Paid. Committed is the signed bid or PO. If you only track Paid, you find out about overruns at the end.

3. Log every receipt the same day, tagged to a category and the property, with a photo.

4. Tie contractor payments to completed scope, not dates: walk it, photograph it, then pay.

5. Re-forecast weekly: projected profit = ARV − purchase − (committed + remaining budget) − holding − selling costs. If it drops meaningfully, stop and re-scope before the next draw.

What do you put in the "committed" column: signed bids only, or verbal quotes too?