Most aircraft (apart from those with single piece wings) can be built in a single car garage... technically. This relies on completed parts being able to be stored elsewhere (suspended from roof, lounge room, etc). Things can get very tight, but it is possible. I've seen others errect a temporary gazebo type structure in their back yard and build in there. Heck, I've even seen pictures of people building their fuselages in the middle of the lounge room... of course, no significant others are involved I dare say.