+1 this ^^ comment. If the founding members don't know how to sell their own product, I think you have bigger problems to solve before you worry about how to compensate your salespeople. (If you do know how, then sell it yourself until you reach the threshold where you can just hire sales people on base salary+commission).
If you absolutely must, bring in a partner (and equity) who will close your first N (for whatever "N" is that makes sense in your situation) sales, that you must close in order to "keep going."
You can tier the equity stake the partner earns (and cap it): e.g., first X sales gets $Y cash commission, next X' sales earns $Z cash + 0.N% equity per deal, up to M% total equity cap.
Edited to add:
The notion that you need to give out equity to keep sales people motivated is a HUGE mistake, IMHO. Unlike most employees, who are income-bound by salary plus bonus (e.g., their salaries don't scale directly based on their performance), equity can be a nice incentive. But, for commission-based sales where income scales directly with performance, a good sales person (who knows they're a good salesperson) knows they can make a killing right now (and thus, don't need the delayed gratification of an equity liquidity event) by just doing what they do REALLY well.
As long as you track sales properly and pay out commissions correctly and on time, making tons of money is usually incentive enough for good sales people.
And, bad sales people ... well, you're gonna want to throw them off the bus ASAP, and giving them equity makes that REAL hard.
