T.S.
Pre-paid legal is a pretty much like selling Mary Kay or Tupperware, only the thing you are selling is legal services. You don't really work FOR them. You buy in and have the services, then make a commission selling them to other people and from the commissions they make when THEY "share the opportunity."
In GENERAL these kind of businesses are bigger money-makers for the early joiners because you need to have people UNDER you to sell too, and THEY have to sell it too for you to really make any money.
As with all of these kind of businesses, if you NEED/WANT the product and are willing and able to pay the start-up cost just to have it, even if you never make any income, then go for it... otherwise, I'd look for another part time job :)
HTH
T.