I am a commissioned employee. I do not get an hourly wage as a massage therapist. Can my employer #1 make me stay at the job site while not getting paid and #2 use benefits as a reason why I have to sit around and not get paid.

The employer CAN require you to wait for walk-in clients. That is known as "engaged to be waiting"; hours worked.
http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_785/29CFR785.15.htm

However, your comission for the workweek, when divided by your hours worked (including "sitting around" at the direction of the employer), must equal at least minimum wage.

Whether or not you are receiving benefits is irrelevant to this issue.

Whether or not you are receiving benefits is irrelevant to this issue.

Federal law (FLSA) generally mandates minimum wage for hours worked but does not say anything about benefits. This is why benefits are a very legally unrelated issue to the rest of your question.