I started last year. I had most of the tools already. I picked 90s ford trucks as my platform: cheap, plentiful, variety of models, known to be reliable, easy enough to work on with simple tools, parts still readily available, lots of YouTube material for any job I need to do.

I bought a couple and I've already had to do a lot of work.

It turns out, it's not that difficult. The systems are simple, each on their own, with few exceptions. When you isolate systems, you can just learn one at a time without pressure to be a whole mechanic. I still reserve the right to send it to the shop if needed.

I haven't had to rebuild an engine yet, but I've been all around the wheels, tires, axels, AC, fuel system, timing, vacuum lines, trailer wiring, brakes, coolant system, and of course I service all my own fluids.

I put it off way too long. My advice is to start now, if you think you'll like it. And you can start with mowers...a whole lot of the tools and concepts transfer.