Business Brokers

My bro-inlaw is out of work now for a couple of months. He's dealing with some health issues and finally getting them squared away. My question is this: He's got an accounting degree but he's looking into an offer that came to him from a business broker. Commission only selling other people's biz. The franschise this guy owns is the #1 business selling franchise in the US. Seems like a good deal. BUT I'm just wondering how tough this business is being all commission. It seems to me business's don't just sell everyday. Are there any business brokers out there? Or someone with experience in this field? thanks... Ron