Finding Sales Staff - Commission Only?

I've had my own business for 2+ years. I'm making very good money via selling local advertising on behalf of local sports (typically Rugby & GAA) clubs. I've had friends and family working on my behalf in the past but at the moment am back on my own. I've got long term contracts with clubs around the country and will soon be in the position that I've too many contracts but not enough time to do them on my own. Up until now I've paid no salary but upto 30% commission on sales. The guys who've taken on the contracts have done well (as have I). My problem is that I've a simple idea, that anyone with some get up and go could replicate. So if I show someone how it's done, they could quite easily (I would in their shoes) carry out 1 or 2 contracts and then go off on their own. Does anyone have suggestions on the best way of finding staff? It's nice and simple when it's commission only - do I have to bite the bullet and employ someone? I don't fancy paying commission to a job agency....FAS maybe?

FAS are good for technical staff but sales? I don't know if you would have much luck with them.
IMHO sales staff (good sales staff) are very very hard to find.
Why not take someone on with a low salary and keep the high commission (say 20% over X ammount). That way you can have a non-compete clause in their contract.