Older laser printers tend to have some pretty good steppers. The newer printers tend to do some magical things with DC motors and optical movement sensors.

Medium old photo copiers also tend to have some fairly hefty steppers. I don't know about newer ones or the very old.

The only problem is that many of them don't have that great a resolution. They often use roughly 24 step motors and then peer that with some interesting gearing. This would not be a problem for many robotics projects.

When you get a typical NEMA17 fitted motor it will often have a resolution of 1.8 or even .9 degrees. Which is great for CNC and 3D printing.

Really the only problem for robotics with the above motors is that you might not be able to find a spec on the pins or the pretty much anything about them. But for some reason I have never had any problem experimenting with this and figuring this out. As for voltages and whatnot that tends to be printed on the motors or you can figure it out from the circuits in the machine.

This last bit might seem hard but actually many printers/copiers have a power supply board that is physically divided into the sections for different voltages. There is usually one fairly high voltage region which might even be separated just for the toner parts. Then there is often another in the 24v range for the motors, and finally something in the 5-12v range for the thinking parts and maybe the smaller motors. The traces on the circuit board get smaller as the voltage drops and the wires get thinner.

So all the usual precautions about avoiding getting zapped. I have happily extracted about 6+ good useful servos out of an office photocopier. The key is to lay down a tarp, don't wear your Sunday best and prepare to be astonished at how much garbage you will generate. If you have a copier that will fit into a large garbage bag, by the time you get it apart it will fit in 4.