>>4476390>example of decent body I can buy used?600D, 650D, 700D all good options that are about the same. Don't go lower numbers, they're older.
Also consider the two digit canons that are still the same sensor size but are bigger cameras with more functions: 40D, 50D, 60D are decent, the 70D is the first in that line with a flippy screen which may or may not be of use to you and you can get a 70D for about $200-300.
But if you're going to pay $200-300 then I actually recommend a 5D II. The single digit canons are full frame which is going to be the biggest upgrade in image quality you can get per dollar. 5D mark I is a bit old but it's "film like" in its operation and output. The 5D Mark II is defintiely the most value:dollar ratio you can get on the used market period and will set you back around $300-400. The 5D II, III and IV are still used by pros these days and I absolutely recommend the Mark II version over anything else you'll buy, so long as you can be fucked carrying it around (it's like 2x the size of the 600D, 700D etc.).
tl;dr
>5DII (recommended) $300-400>70D (APS-C recommended) $200-300>600/650/700D $100-300 