I think there are better ways to learn, rather than going into the expense of a used car, unless you get it for free. If you get a lemon you will end up getting even more frustrated because repairs open up more repairs. If you are really inexperienced, you might waste a lot of time getting into things that are over your head, like exhaust work without a blow torch.
Instead, I would encourage you to get with people who have more experience to start you in your learning, maybe helping other people work on their cars as an alternative.
Get a good basic set of tools (talk to experienced people on what you need), get a manual specific for your car, like a Haynes or Chilton, and start out doing the more simple tasks, like oil, filter changes, and tune ups. Don't start with an engine rebuild or trouble shoot electrical issues, unless you have a background with the latter.
Use forums, like this one to ask questions, watch you tube videos specific to the task you are wanting to accomplish, like Eric the Car Guy (read a manual first though on the task).
Get with an auto club if they have one for your car. I met a man who was a beginner with auto repairs and joined a club for Mazda Miata's. He was able to change a timing belt early on because he had over a dozen experienced people helping him at their monthly meetup and repair meeting. They would get together and just work on cars all day on a Saturday. Personally I really like this idea of getting together with others for help, if possible. My neighbor and I do this regularly, even if it's just to talk about how to fix something or borrow tools. I have another neighbor that likes Ford Mustangs and he and his racing friends regularly get together and work on cars.
To sum up, there is a lot to know and learn so you will have to invest time and money into it, but it will be a lot less than paying to have the work done. I just spent hundreds of dollars on emissions work for parts, but it would have been a lot more at a shop.