My 'sweet spot' was the late '80's early '90's. I was able to pick up cars all the time for less than $200 and a lot were free. Now, granted, I'm talking about basic family cars, not muscle cars, but still. Most would be considered beaters, but a few were really nice.

At the time I lived in the tri-state area of NY, CT, MA. MA had strict laws about NO frame rust on cars, CT was the same way but with the added burden of having to pass emissions too. NY just expected the car to move and stop under its own power. Back then, people usually had to pay to have their car hauled to the junkyard. Yards paying you for your junker weren't around. People would have a running car that they couldn't register anymore because it wouldn't pass inspection and they couldn't easily sell it, so they'd end up kinda stuck with it. Then a lot of times, they'd get fined for having an abandoned car.

People just wanted their headache gone, and were usually more than happy to unload it on me. My only stipulation was that it had to run (I didn't have a way to tow a car). I would take it back to my little shop I was renting in CT, and evaluate the car's condition. Too far gone, it got parted. Minor repairs, I'd register it in NY and sell it. Being that I usually just dealt with Mopars, parts would often come from other cars I parted.
Then, as now, a neighbor ended the fun. Had a visit from the cops one day. I kept the outside yard clear. If I had to park something outside, it was on inflated tires and not jackstands, no parts strewn about. Gave me the riot act of how I was running an illegal shop, didn't have proper licenses and permits.

I never pursued it further after that. I kept what I wanted, got rid of the rest and less than a year later moved away. Ironically(?) the same town that I was in that was so against 'old cars' ,now hosts an annual car show/cruise in.