Many new folks to hosting and the web site industry tend to assume if you have a site you can make money. Although this is not impossible, but in all likely hood this is much harder than most people think.
Even if you have a good name, a nice looking site which I might add most are far from nice looking and often lack professional programming, look, and layout.
If your site looks like a 3rd grader did it than don't expect anything.
Is your site unique? No well you might think about coming up with something new or exciting.
What do you got inside? Anything? A little? Not much?
Well why would I pay to join your site, when there are tons of free sites out there with unlimited content? Some I may have to join, but they are still free with a wealth of content once I join.
So the bottom line is yes this is exciting, but unless you have something unique with tons of content to begin with I honestly don't think you are going to be able to charge anything. Without bursting too many bubbles this is how it is. I might see how an adult oriented site might charge a few dollars per month with tons of content inside, and updated regularly. This is even skeptical as there are so many free adult sites.
Only other thing I can relate to is google or other ads. You hope to attract a bunch of visitors and hopefully they will click on some of them. You certainly aren't going to get rich but at least it's something.
Otherwise maybe you sell, create or program something big time. For most this isn't a reality either.
All I can recommend is offer free membership. Build your site up with content, thoughts and ideas. Get others involved and build it up. Only then you might, and I say might consider charging a fee.