Usually support staff is paid either monthly, per client, or per ticket. I don't think that anybody will work for free web hosting, and support staff don't bring in sales, but even if they did sales as well, 50% commission on the first month on one of your packages is just a few bucks. This seems sort of fishy, why can't you just pay them normally?
Geez, give the guy a break. If the offer doesn't interest you, pass on it.
And with my own small webhosting business, I hardly EVER get support requests, even though I have a full server. So, if I had a support person, they would probably be better off with free hosting, rather than a per ticket basis.