Depends on your region, but the cheapest no bullshit printer is probably any prusa. Anything cheaper and you have to be able to take apart the frame, manually square up everything, measure your diagonals, etc. If you get an ender or anything that uses the creality electronics you have to make sure that the wires in the screw terminals are not tinned (solder on the ends) and clip them and either put them in bare or crimp ferrules. It's a potential fire hazard and at least one person has reported experiencing that potential. Plus you end up tinkering, upgrading and tweaking more than printing which probably wastes any money saved by getting a cheaper printer.

Source: I have two ender 3's and they don't look like ender 3s any more.