Somebody offered me three contracts and I have no buyer list at all

11 names isn't a list, it's a start. The thing I'd want to know before you say yes is whether those 11 have actually bought anything in the last year. Two flippers who follow you is different from two flippers who closed three deals each. Have you asked them what they buy? Price range, area, condition, how they fund it?

If you can't answer those for at least four of the 11, you're not selling contracts, you're cold calling with extra steps.

Take the 12k one only.

Reason: if you take all three you'll spend your 21 days spreading thin across three price points and three sets of numbers, and you'll blow all three. If you take one and blow it, you learn what broke and he'll probably still talk to you. Wholesalers who can't move their own deals are not short of options, they'll be back.

Also ask him why he can't sell them. Sometimes the answer is he's bad at dispo. Sometimes the answer is the contract price is wrong and no buyer on earth wants it at that number. Those are very different problems and only one of them is yours to fix. Get his ARV and rehab estimate and run it yourself before you agree to anything.

The 40 percent number is worth a second look. You're doing the harder half of the work on a deal he already couldn't sell, and taking under half. I've seen the split described anywhere from 30/70 to 50/50 depending on who brought what, so 40 isn't outrageous, but it also isn't a favor he's doing you.

Separately, and I don't know your state, but check whether marketing someone else's contract to buyers puts you anywhere near activity that needs a license where you are. That varies state to state and it's a question for someone licensed in your state rather than for this thread. Worth knowing before your first call, not after.