I had a 5D and have a 5D mk3.
(The mk is the version number)
Both take excellent photos, especially in low light. I reprinted some of the original 5D photos 11”x17” and even though they have fewer pixels the quality was fine.
Canons are pretty cheap on the used market because they have a new mirrorless R series cameras/lenses so the older ones value dropped a lot.
A good lens helps a lot. Someone on the thread suggested a 50mm 1.8 “plastic fantastic”. It’s a great choice. Really sharp, lets a lot of light in, feels kind of cheap. I always liked the 24-105mm f4 zoom, but it’s pricier.
Cannons are no longer pretty cheap. If so then they have huge mileage on them, shutter count might kill your camera soon. I think the window closed two years ago and now they are becoming very cool again.
Besides the 50mm nifty fifty. There is "middle" range of "ultrasonic" zooms that are actually pretty capable and underrated/cheap. I have few for canon film cameras and their secret huge advantage is weight, optics wise they are pretty good (i have them converted on lumix full frame). I would also mention sigma 35mm art which can be get for less than 300eur and is THE lens if you know you like 35mm (person i ended up being).