That depends. Depending on the type of business you have, you could indeed pay on straight commission providing the commission is equal to or more than minimum wage for your state.

If the employees are not full time and pass the IRS test for "Independent Contractors" you could pay them in that fashion as well.

If they are true employees, they will be subject to Wage and Hour regulations so unless you have them engaged as a contractor, you would not be able to pay them on a piecemeal basis.

You should review these rules and regulations at the website for the Department of Labor: www.dol.gov

Feel free to contact me for further assistance.