Whoof... I would not recommend doing a full boil inside an apartment if you can possibly avoid it. You're basically putting a gallon or two worth of water into the air. Things will get muggy quite quickly.
Presuming you can't get a natural gas hookup, you'll be restricted to butane burners; propane gives off too much carbon monoxide. Even with a butane burner, I'd advise you to buy a CO detector if you don't already have one.
(As an alternative, you should consider electric heating elements. Personally the idea of doing the boil in a plastic container weirds me out, but I know a lot of people use that approach, and there's a definite convenience advantage.)
Beyond that, yeah, the only real issue is BTUs. The only other thing I'd pay much attention to when buying a burner is windproofing, and of course that won't be an issue indoors.