I certainly appreciate your drive to gather information
I have posted before, my criteria for judging MLMs. In my book, they are bad if they satisfy any of the following: (I will explain why if you are interested)
1. Require you to buy product to be a distributor.
2. Require any “training” for the job.
3. Require you to “qualify” at some level(in recruitment OR sales) in order to get commissions.
I am not personally familiar(other than this forum and google) with Mary Kay or Avon, Tupperware or the jewellery thing – but I’d be interested to know if they meet any of the above.(My attempt to gather information).