It depends on how people want to support the forum I think and if it's reasonably priced. Is it a good income where you could live off of it? Probably not.
I would probably set something up where it's X amount of dollars to say, get your name color changed but if you don't want to spend money you could post enough on the forum and pay X amount in forum currency to get it.
I believe there to be other various perks that could potentially be in place. My favorite (if it was effective in this day in age) would be to place an Ad or two on the site and then people can pay a small fee in dollars each month or perhaps even a determined amount in forum currency a month both benefit the forum in some way.
I do not think that I'd be necessarily trying to make a living off of it though.
Well, it is possible, of course, to get a small income to fully or partially support website costs only. However, that too can be hard sell, simply cause so many people are so, well, sorry to say, stingy.
😛 But then again, is it fair for a few generous souls to pay for people who have the means to pay?
OK, this would evolve into a paid membership vs donations thing - but there is no
chance in crap anyone will pay to join - even a great forum, normally.