Hi Nanna, the 101 was Singer's then top-of-the-line machine, and their first with a direct-drive, or "potted" motor. That means it has no belt; the motor drives the shaft directly via gear.
However, I would almost always pass on a 101, even if one were offered to me for free. Here's why: The model 101 is from the 1920s. That's nearly 100 years ago, and the chances of the wiring being intact are virtually nil. Which means the machine will need to be rewired.
Even if by some miracle the machine had been stored for 90 years in a perfectly climate-controlled environment, and the wiring was perfect, I'd still need to disassemble the machine and open up the motor to look at the wiring and figure out that it was okay. And that's a lot of work.
If your priority is historical restoration and renovation, the 101 might make a good addition to your collection, for the sake of being comprehensive. If your priority is to sew, you might want to think twice (unless you're willing to disassemble, inspect and re-wire, or pay someone to do the same).