Sorry guys! got tangled up between threads!
What I meant to say is this:
Commission only can work, but keep an eye on how well the salesperson is doing.
If they sell lots you'll be paying out a lot in sales commission. That's OK as long as you can fulfil the orders and pay the commission - everyone wins. Don't be tempted at this stage to change the terms of the deal with your sales person - it's not fair and, after all, they're bringing you in lots of lovely business.
If they don't sell lots they won't earn enough and will be off, maybe at very short notice, so you'll be without a sales team.