Can we change our down payment amount once it appraises

[Jessica Long]

Hello! My husband and I have been given the opportunity to buy his parents home at a deep discount which we will live in as our primary residence. We are trying to use a gift in equity to cover the down payment and closing costs (we need to keep as much cash on hand for renovations and a side venture). 

Since we are guessing on what the house will appraise for, is it possible to change our down payment amount once we find out what it appraises for (we will buy at appraisal value and get the difference as a gift in equity between that amount and the actual desired sales price of the owner). We are very open with our lender and still considering other lenders but he’s been a bit confusing or we don’t know enough and so it’s unclear what the answer to this question is (maybe it differs between loan officers?).

Please advise! Thank you