I've had guys who were mobile - one was in Costa Rica, he drove an old mercedes universal (station wagon) full of tools, and he did work in my carport, and another guy here, in VA - this one has couple of trucks, one is light duty with some tools, and the other one is a rolling tool shed on heavy duty chassis...

He works in my driveway, and he prefers me getting the parts, as he doesn't have "business" relationships with the suppliers... It is like a DIY, but with hired hands - I even helped both guys, something light, like holding a light, or handing a tool over... Some repairs I could have done myself but I figured, I'd pay the guy and have him do it in half the time while I am watching and learning...

Very little overhead, as they have their tools, they don't maintain business location and don't pay rent... Of course, they were lacking some of the things that the big boys have, like big lifts, or some heavy machinery but a lot of work can be done without those big things...