I've done some research into the business this man has gone into. I'm glad he hasn't paid much to join when I find this article on Wiki about multi-level marketing outfits
The outfit he is joining is listed as one of this type. Hardly anybody makes any profit at all. His company may be one of the better ones, but we'll see.
As part of our conversation, I did say that it was always advisable for people to research the product and market before starting a new business, and gave him a couple of actual clients who hadn't and had lost money as a result. So he can't say he wasn't warned.