If you feel you are handy, I would buy a cheap pin and learn on it. If you mess up, not big deal. It does not have to be your dream pinball game, just one to play with and learn on. You can always sell it later.
Pick a very common manufacture. Any of the early Bally SS pins would be ideal. Lots of them were made and lots of info on fixing them, parts are cheap and easy to find. Just don't get one that is super abused, likely too many problems and you will get frustrated with it. I learned on two Ballys I got as a group buy, both dead but not abused. They had worked, but were left for a few years unused and now did not work. These were ideal machines to learn on. Have two I could swap parts back and forth on was also very handy for diagnostic work.
Read pinwiki and/or Clay's manuals and you should be able to get almost all of your questions and problems answered. Anything really weird or if you don't understand something in on of those two resources, post here.
I think you will find it very challenging to be in this hobby if you don't have at least a basic level of "fix-it" ability or deep pockets and great local repair person. Even if you do have a great local repair person, do you really want to wait for them to work you into their schedule to fix a game only to realize it was just a wire that fell off of a flipper coil? A repair that will take you 5 minutes to do on your own.