salary, company vehicle, health benefits and a precentage of gross sales is the norm according to the most recent ALCA Salary Survey.
Salesman is not responsible for achieving profitability if they work off of a pricing schedule you supply (yes, I know it's difficult to swallow - but it's true). If you want to tie commission to profitability, it'll be better for your company, but you still accept the risk if the job is not profitable. If you pay a percentage of profit, then you have to have a program in place to track costs in order to know profitability.
They NEVER think like an owner. Ever.