How much would you pay montly for a MLM plan?

no too many scams out there

You shouldn't pay anything for the plan. That would make it an illegal pyramid. What you pay for are the products or services you use. And maybe a small monthly fee for a Website. When you find customers for the products or services you will not be paying anything. You'll begin to make a profit. And that's why you want a business isn't it? Find a product that reasonably priced that people want and you can be in profit the first day. I always tell my new people to focus immediately on selling product. And it works if you do!

i never used multi level marketing (MLM)

I am in MLM (multi level marketig) which also is called network marketing or recommendation marketing. Your mentioned 15$-monthly network only will work on the long run, if people get something for it, what they can consume .... say a service or a product .... but it must be of a high quality and they really must need it .... if this 15$ only are paid for staying in the network, then it is just a pyramidal system, which sooner or later will die .... in this case the 15$ are just feeding the upline and the whole thing is a scam.