Cost is obviously a big factor. Almost every printer can change to any nozzle size and layer height for just the cost of the nozzle. Print volume is a major limitation, depending on your use case. The filaments it can print will probably be the same across any relatively low cost printers, with the only significant change being direct drive vs. Bowden.

Bed leveling is huge, and makes probably the most difference in print quality on low cost printers these days. If there’s an easy way to tension the belts, that’s a plus. If there isn’t a power switch on the front (or even if there is), a emergency stop switch can be a help, like if the nozzle is running into the bed.

Maintenance varies from printer to printer, generally you’re aiming for tight but not too tight on any belts or rollers. If the pulleys on the motors aren’t preinstalled, use something like loctite blue to fix them in place better.

Also make sure if you plan to buy a printer that it’s got a decent amount of community around it. Running into the same problems with a bunch of other people is a big plus as a beginner, so popular printers are better.

Teaching Tech made a calibration guide website that I’ve had a lot of good experiences with.