So this may be late to respond but like…I shoot still photography and spent $50 on a used Nikon D60 (2008 era entry level DSLR) as an experiment to see if I could get images as good as my Nikon D5500, cleaned it up, and surprise surprise, it works just fine. Image quality is comparable if you know what you’re doing (I got it at MPB.com, by the way). At 10 megapixels the sensor leaves plenty of room for cropping if you make a slight mistake or whatever. I’ve also picked up a few inexpensive older lenses there- and same thing, no need to spend a fortune on new gear, especially if you’re shooting DSLR. Used gear completely changed the game for me.
I would recommend if you go MPB getting excellent or like new condition on the camera body though regardless of what you do.
Mirrorless I can’t talk about, but I do know it’s way pricier. As a final note I’m ironically using the D60 exclusively for now because it’s simpler and I’m teaching myself all the old film theory and other things I didn’t learn properly about cameras with a simpler camera before I go back to the more advanced and powerful gear I shelled out on years ago. I’ve learned so much doing that so fast it isn’t even funny.