With 20% down, can seller concessions go up to 20% as well?

Not quite. Conventional seller concessions are tiered by down payment and top out at 9%, so with 20% down your cap is 6%. The Fannie Mae and Freddie Mac tiers for a primary residence or second home: - Less than 10% down: concessions capped at 3%. - At least 10% but less than 25% down: capped at 6%. - 25% or more down: capped at 9%. - Investment property: 2%, at any down payment. The other important piece is what concessions can actually cover. They apply to eligible closing costs and prepaid items (things like escrows for taxes and insurance), and they can also go toward buyer-agent compensation, which is negotiable. What they can't do is reduce your required minimum down payment; that money still has to come from you or an allowable gift. So concessions are a strong tool for cutting the cash you need on the cost side, just without touching the down payment itself.