I used to do network marketing and have in the past purchased leads. I haven't done the business in over 2 years now (and have no intentions of ever getting back into it).
Anyway, from my experience, there is a huge difference in the quality of leads you get. You really need to know how they are generated and make sure they are REALLY interested and didn't get any incentives for filling out forms. The more information you get about them the better. You want people who are really interestred..not people just filling out forms. Also, IME..it is very, very, very dificult to build a business using networking leads. Some people can do it, and are very sucessful..but IME those people have the gift of charism and have that magnetic personality which draws people to them. If you don't have that, it is very difficult.
I woudl just look at how the leads are generated very carefully, look at the success of others iwth that source, and really think about if you have the personality, persistance to really work a business that way. It is very hard work, very discouraging, and I was never good at it.
I might not be thinking about this the right way. When I say "leads" I mean a bunch of business people get together to help each other in business. The leads would just be people they know, not mass leads they got from drop-boxes. Am I just calling this the wrong thing?