Outside sales reps

How many of you have an outside sales rep? I am looking for one right now, and am trying to figure out what a proper commission should be. A certain percentage on leads that I generate, and a higher % on leads he/she generate. Also, more money for a sale over and above the min. S/F price. Any thoughts guys/gals?

We provide them a company vehicle and cell phone, and give them a base salary ($1,500 per month) plus 10% comission on whatever they sell over $5,000.

I Just give 20% of the sale he makes, phone, and some petrol €€ and food vouchers! He's doing more 2000€+ average a month!