The loan is against a house that does not exist yet
A renovation loan is unusual because the value it lends against is the value *after* the work is done. The property in its current state would not support the loan, which is the whole reason the product exists.
That single fact explains most of the rules that follow. If the lender is lending against a finished house, it needs strong evidence of what finished means, and that evidence is the contractor’s scope of work and bid.
What underwriting is actually reading in the bid
A usable bid is itemised, priced line by line, and signed by a contractor who is licensed and insured. A one-page total with no breakdown will usually come back for rework, which costs days.
Underwriting is checking that the work described actually produces the value the appraisal assumes, that nothing structural is hiding behind a cosmetic line item, and that the timeline is realistic.
A contingency is normally built in on top of the bid. That is not padding. It is what stops a mid-project surprise from becoming a funding problem.
Draws are why you cannot self-perform on most programs
The renovation money does not arrive at closing. It sits in a draw account and is released in stages as work is completed and inspected.
That mechanism is built around a contractor of record, which is why most programs will not let the owner do the work themselves. If you were planning to self-perform, say so at the start. It changes which programs are open to you rather than being a detail to sort out later.
Where these files actually go wrong
Almost never the borrower’s credit. The common failures are a bid that arrives late, a scope that changes after the appraisal is written, and a contractor who will not provide licensing or insurance documentation.
Each of those is fixable early and expensive late. Getting a real bid in hand before the file is submitted is the single highest-leverage thing you can do.
The fork that decides everything else
Occupancy sets the lane. A home you will live in is a consumer loan and available in select states. A rental you intend to hold is business purpose and available in nearly every state.
If you are buying to renovate and sell in a matter of months, this is usually the wrong product. That is bridge financing you refinance or sell out of, not one permanent loan with the rehab inside it.
Programs, draw mechanics and eligibility vary by lender and by scenario. Nothing here is a commitment to lend.