Pretty easy question. You can ask the seller to pay for all of it, you can pay for all of it, or something in between. If you're getting a screaming deal, I wouldn't suggest asking the seller to pay. If you have a problem financing the reroof, you can do what I did. I bought a 17,000 sf mixed use building for $100,000, a SCREAMING deal. It needed a new roof at the cost of $25,000. Since I was getting such a great deal, I did not ask the seller to pay for it, but instead increased the sales price to $125,000 and had the extra $25,000 put in escrow for the roof. Neither the lender or the seller had a problem with this. The seller got the same net capital and the lender got their collateral improved.