I would advise your friend to visit various Dealership Service Departments and speak directly to the Service Managers and find out if they would consider this; as well as local national service centers (Big Als, Pep Boys, Walmart, etc…) and local privately owned service stations…
He is an “Un-Proven” service provider and if one of the aforementioned did offer a carburetor rebuilding service where they remove the carb and provide it to your friend to be rebuilt, the customer’s car would be out of service all the time your friend has the carburetor and they would have to store and secure the vehicle until your friend finished with the carburetor. They might not be so willing to take on that responsibility until he has a proven reputation…
What your friend would be doing is different from the young woman’s business, where the customer takes the carb off and sends it in, she might even have some commercial accounts, but I guess from the article, it’s more a private business affair…
The reason I bring this up is that I have some experience with this. In 1995 or 1996, when I was stationed at Goodfellow AFB in San Angelo, Texas, my wife’s '85 Toyota Corolla needed its carburetor rebuilt. The sole Toyota Dealer in town was Mitchell Toyota and I was a friend of the Owner, Mike Mitchel, and I had a lot of respect for the Service Department. However, they would not take on the task. They explained that they had no one qualified and they did not recommend any local business either. They said he had a shop in town that did the sub-work for them but with various new employees, they had received several bad jobs that could not be fixed and they ultimately replaced the carbs with new or rebuilt ones from their service department, so they just completely stopped any and all carb work…
So, before your friend invests his hard earned cash or too much time, he needs to know if these businesses are even interested in him providing this service…
Remember; many of the members have posted stories where they could not get various items rebuilt and the only service offered was an R&R (Remove and Replace…).