In addition to the consideration of the number of locomotives you will have on the track, as gcodori has pointed out, another consideration is the wiring system you use to connect the track to the command station/ booster.
Typically, you will run a 2-wire track power buss of a minimum thickness of 14 or 16AWG around your layout - the thicker the wire, the better. One end of this track power buss is connected to your command station/booster. The other end isn't connected to anything.
From this track power buss, you will run track feeders up to the track. The more track feeders you install, the better. This is because there is electrical resistance in the rails which drops the voltage as you get farther out from the track feed - like your traditional toy train set, as gcodori has pointed out.
If you have locomotives that draw a low current, a good track power buss with lots of track feeders, you shouldn't need a booster on your home layout.
For more information, go to this page on my website and scroll down to "Laws of DCC - Law #3"
DCC Laws
Bob M.