Hello Juan
I have a PSR-2100, that I have had since 2003. Never had a problem with it.
It is a very good keyboard, and I still have mine, and it is working perfectly.
But keep in mind that it has a FLOPPY DISC DRIVE, and you must check if this is working, or you will not be able to import styles or MIDI files to it. If the floppy disc drive is still working, the problem is to get floppy discs, as thesa are becoming rare now!
It may be that they have changed the floppy disc drive with a floppy disc emulator. You will then be able to use USB sticks, but the emulator functions in a certain way that can be complicated. Another problem you may get is that the light behind the display may fail. It can be replaced with LED strips, but you have to have a good deal of technical skill to do that.
If the price is not too high and they give you one year warranty, that is positive. But if you only are after the sounds, I would check if those sounds are not on your keyboard, in the legacy folder.
The 2100 is special, I love mine, and will never part with it, but I have newer keyboards that I play every day now
Let us know what you decide
All the best from Toril and her PSR-2100