Ive been asked to invest 50k

for a web cam studio start up. as an entrepreneur I like the potential roi. I am hoping to gain some knowledge. First some assumptions on the plan:

1. they are serious business men
2. there is a niche they will have with the models
3. The overhead for in-house models is low
4. they want to develop a proprietary intelligent chat software for converting guests into paying members
5. am being told that we will earn 50% of what the models generate for a site that provides the members, traffic, name recognition...
6. P & L states that each model in a 6 hour period will generate 60 minutes of pay time.

So this is part of what I know in the plan. I am looking for some advice on this information.

Is 60 minutes out of 6 hours great, average, or unrealistic?
Which are the best sites to get signed up with as a studio?
is 50% good or standard or what?
Do any of the existing sites have software with an open API?
What is the hardest part of starting a studio of this nature?
What is the biggest reason studios fail?

I really appreciate any and all feedback.