There was a shop in Portland Maine called the Monkey Wrench Auto Shop that had a program like this. They eventually dropped it and they closed down after many years of offering mechanic services. Some military bases have hobby shops that operate the way you want. The car owner rents the bay for a day or a week or more and rents the tools he needs and gets advice from the shop personnel. This is all underwritten by the US Government and the liability is not a problem.
Starting this type of facility would require buying or leasing a multi-bay garage, Purchasing a lot of special tools, creating the legal rental agreements that would hold you blameless, securing knowledgeable support staff and advertising the shop.
Perhaps opening an auto school where people could come and take part in seminars that last only a half day or a few days that explain one specific repair. you could open an auto parts store with a shop and set aside a few bays to be operated as a hobby shop.
