a4android is right, but to give you the detail as to why;
The important point to remember here is that black holes don't have infinite mass. They have infinite density. That means that a black hole can exist with (say) the mass of the earth, and orbit our sun even at the same distance from the sun as Earth, at the same speed as the earth, and maintain a stable orbit.
It's the mass that makes things possible to orbit each other, and the only reason why the mass of a black hole increases is that it sucks other things into it's gravity well. BUT, that's no different to our own sun in many respects. The reason why the Earth orbits the sun is that the sun is sucking the earth into it at the same rate as our momentum is pulling it away. If we didn't have that momentum, the Earth would have been sucked into the sun long ago. Ironically, the reason why the Earth doesn't get hit by that many asteroids and comets is that Jupiter pulls in a lot of the detritus in the outer solar system, protecting the inner planets.
So, the only difference between a black hole and a sun or a planet is that by comparison, it's very small. In all other respects, it's just like any other celestial body in that it has a fixed mass that only changes as it pulls other things in or loses mass through collisions or radiating out heat.