You can never tell really, until they meet each other. We adopted a kitten in the summer, and at first I thought we'd made a big mistake, all our adult cat did was hiss and growl at MKitten. Now they're like proper brothers, palling about together, doing cat stuff. They're a fair bit of rough and tumble, but all done playfully.
IME boy cats are more easy-going than the more dominant females.
I generally think it's a good idea, particularly if he stays inside and you aren't around all the time. Whenever you introduce a new cat it normally takes a while for them to tolerate each other, and longer still for them to become friends, but it generally happens eventually (the former if not the latter). And if you get a rescue cat that has been shown to actively like other cats then that's half the battle won already.
And there are so many cats desperate for homes that if you possibly can offer than then it's got to be a good thing.