Their rural home loan guarantee program has upper income caps, so check with a mortgage resource to see what they are in your area. There are also some charts on the USDA site here. I just closed a loan for a teacher on a $218,000 purchase, and she got in with no down payment and even got her $500 earnest money deposit back at closing.
What we did was to negotiate in the purchase that the seller would pay 3% toward the buyer's closing costs. With the 102% financing, and a good appraisal of course, she got the entire purchase financed, and at a great rate, only 1/8 percent over the best quoted 30 year rate at the time.
Sometimes the difference between a goose egg and a commission is just finding a way for your buyer to get what they want with what they have to spend. Check out the USDA rural loan program for your buyers who qualify.