I have to agree with @orangethirty comments on this page. There is not enough margin in the auto service business to let this succeed. I have known people that washed cars professionally in both small high-end detail shops and full-size car wash operations. The high volume car washes are staffed largely with people that could not get better jobs - felons, drug abusers, those with no education or other job skills. The small high end detailers were generally guys that loved cars and found happiness in polishing a Porsche for an afternoon. There was an old guy named Al that used to come by my office and spend an hour on my truck for $30. I don't know where he went, but I miss the service. You do the math on what his income was per year if he had to travel, pay for soap and supplies, and then only grossed $30 per hour. My math estimates that he couldn't be netting more than $25,000 per year.
YourMechanic will also hit this same problem. They promise 30% savings and at-your-door service. This will run into the same issues. There is not 30% margin to cut at any small auto repair shop that I have ever dealt with. For those keeping track, I sold equipment to 200 auto repair shops over a ten year period. There are many car repair problems that are not fixable in the field. The bigger problem is that auto mechanics have the same rockstar ninja aspects as software. The rockstars simply will not be doing brakes in the rain, outside of your work in the parking lot. Why would they? They can earn $100K a year at a dealer, there is no way they are going to earn less in your parking lot. In worse conditions. In the rain.
Ask the question in a different way. Would you prefer to work in a heated/cooled work environment with restrooms nearby, a break room, a place to wash your hands, specialized tools and equipment nearby, support staff to get your parts, queue up the next job, a counter guy to deal with the customer OR----- would you like to work in the rain, deal with angry customers, no restroom, not enough tools or equipment with you, doing jobs that become much harder because of location, etc etc all for 30% less money? You will not get any talented person to work for you. They have better options. Auto repair is very talent driven, especially any area that is hard like diagnostics, transmissions, or solving the problem that the last 3 shops couldn't figure out.
You wouldn't expect to produce good code in a parking lot, would you?
And then there is the classic problem of auto repair. Once you touch the car, the customer finds all sorts of things that YOU apparently did even though you didn't. Scratches, dents, missing items, the list is long and familiar to all.