I don't consider anything in the $20,000 price range to be "affordable", personally. Spending that or more for transportation is a luxury, plain and simple.
Here's a plan you might not like at first, but it may grow on you when you start really thinking about those monster car payments. I used to be a GM guy. But I got a '77 Bonneville once and it really turned me off to GM. It wasn't just a lemon, it was poorly designed from top to bottom. I switched to Lincoln/Mercury after that. Big ones! Never been sorry since. I've noticed that most GM owners get the same type lemons that I did, but they turn around and buy GM again! I don't know, you figure it out!
So, the plan would be to buy a more rugged used car. Even a nice Cadillac with a 350ci V8 would be a good choice. Any engine in a Caddy, other than the 350, would be more of the same troubles he's having now. But I'm actually thinking along the lines of a Mercury Grand Marquis. Don't take my word for it. Check their track record with your local police (LTDs), or any local garage or even Consumer Reports (gag).
Besides, you can put a replacement engine, transmission, brakes and paint job on any old car for about 18 month's worth of car payments! Bail on the Chevy, buy a nice used Caddy, Lincoln or Mercury and save your money!