JamyeP is right.
a contract is presumed valid and enforceable until a suit is brought and a court says it isn't....
However, since you and the other party are entering into a contract that breaches a contract that both of you have with Facebook. the contract is likely to be thrown out of court.
You give the other party $1000 to Mr X to take over his webpage and run it with his assistance for whenever. After a couple of months you find Mr X more and more difficult to contact until finally the page fails and you go broke.
You sue for your money back. Mr X countersues for the ongoing payments you stopped making.
The judge says: "Ms Knight, Mr X, you both new that this contract was against the rules of Facebook. Ms Knight - you don't get the $1000 back. Mr X you don't get any more money. Now both of you get out of my courtroom."
That's my opinion.
You'd really have to be stupid to even think about getting into this deal. And if you are already in it and have paid money to the other party you are very likely to end up screwed.