Infomercial businesses? I have never heard of that and would
definitely be cautious. I have never heard of ANYONE doing one of these, let alone making money doing it.
However, Network Marketing (MLM) is totally different. Warren Buffet purchased three network marketing companies and said it was the best investment he ever made. Donald Trump even said that Network Marketing is a viable and lucrative business option.
That being said, you must still
proceed with caution. Not all Network Marketing companies are good...in fact many are not. I have been fortunate to be involved with two reputable Network Marketing companies. The first one was Mary Kay. (A front loading, stairstep, breakaway compensation plan.) I earned the car and everything - but it was an old pay plan that required a lot of work, for not a lot of pay. AND...you had to really love sales. The second one, I am still involved in. It will be two years in February. I love the products and can do most of my work from home. I consistently earn $3000-$4000/month - and I know a LOT of people doing the same and more. (New generation binary comp plan) There is a lot of benefits to residual income - it allows me the "bad" days.
My advice: Stay away from TV ads and do your homework if you decide to get involved with Network Marketing. It's not for everyone, but it is for me. There are four basic comp plan structures. Many involve several "hoops" that you must jump through to "qualify" to get paid. You don't want to get involved with anything that requires an "investment" or an inventory.

Also, be very cautious if all they can tell you about is the TOP people...ask them, "what are YOU making?" Be sure the company is well capitalized and run by people that understand being in the field. Check out their track record and ask a LOT of questions.