When you sign a contract there should be a fix limit fee. After inspection, you will give the owner a list of items need to fixed. If the cost for fixing all the problems is less than the fix limit fee, the owner either can fix them or credit you with the money. If cost more to fix the problems, the owner still can fix the problems so you can close the deal. If the owner refuse to fix the problem, you can withdraw from the deal and get your earnst money back. I don't think you can negociate the price after you sign the contract.