Keep in mind that very few shops are "full service" ..even the dealers around here don't typically do automatic transmissions or engine rebuilds. They may yank and install ..but they don't have the idle time available for the space typically. Many shops are fanchise muffler and brake shops ..which you needlessly pay a franchise fee for a name and a sign. There you are buying yourself a job. If you have a good bending machine, and a craftsman that knows how to use one, custom exhaust work demands a premium around here. Money making in brake work is only limited by how fast you can process the cars ..frequently being faster and almost as cheap to throw new rotors on the vehicle then cutting the old ones.
A lube center would be miles ahead without the substantial financial commitment required for the franchise fee. In those, as with most franchises, the value to the owner is mostly a tax shelter and they don't have to make a living off of it. The value is added in the advancing cost of future franchises. It's the same for Subway, Quiznos, McDonalds, Dunkin' Donuts...any turnkey operation. For an individual, you're buying yourself a fairly low paying job ..that if you have the investment capital required for the franchise fees..you have no need working at (you're further along than anything you can possibly make working it).