linking buyers with sellers

I sat down, did a few of the ropes as if it was a regular task and thought about the process.

not if im the in between guy, arent i able to charge both the seller and the buyer as a handlers/sellers fee?

its just a curious question that pepped into my head cuz if im finding buyers, all the while finding sellers, why a 1 time fee? I mean im sure theres a way to pull it to where its ran as a servicing fee to both partys, and me doing the work is the service....