HELP Brainstorm--Exclusive rights to sell

I have some things set up like a real estate broker would( exclusive rights to sell, not a real estate agent though) . I have contracts for exclusive right to sell. I have found some channels or selling that are really working out great. I want to expand. Everything now is local. In order to go out of state, i can make a client sign a contract blah blah blah, but if i am not there at time of sale how do i protect my self (get my commission?). At time of sale i have it in the contract they own me X amount of dollars, locally i am there at sale, but how can i do it when im not there. The client can lie ( say they didnt sell it ) they can just not answer me.

I know there are alot of creative, smart people on here. Any suggestions will help. If you do not think its possible to do it just say so. Also, i can sue them, buuut i dont really want to deal with out of state law suits, because im sure most people will try to stiff me.