I realize this isn't what you meant, but some people have gardens to supplement their food supply and some people repair their own car. I'm not a car owner, but I do repair my own bike and the reason for it is that the required parts and tools are usually much less expensive than a one-time repair (with the biggest expense, tools, being spread across multiple repairs).
As for the regulation of health care, it exists for a reason. Some of those reasons are for the public good. You only need to look at alternative medicine to understand that there are a lot of snake oils salesmen out there. Letting people portray themselves as legitimate doctors would only muddy the water. Then there are factors such as competence. It is difficult enough to deal with in a regulated system, never mind an unregulated one.
One can argue that there are valid reasons to regulate health care. But, as I pointed out elsewhere in this discussion, similar reasons exist to regulate food, and we do regulate food for those reasons, but that doesn't prevent us from having free market competition in food suppliers.
Basically no one in the First World grows enough calories in their garden to make a significant difference, and repairing your own car nowadays generally requires buying lots of expen$ive test equipment. The days of the shade tree mechanic are sadly long over.
Restaurants, yes. But supermarkets and car mechanics? Everyone has to eat, and everyone who has a car has to get it fixed sometimes. In fact, people need to eat much more often than they need health care--yet supermarkets are somehow able to provide a wide selection of food at reasonable prices. The same could be done for health care if it were a competitive free market instead of being regulated so heavily.