the kx is still current. nothing too redeemable about the rm though
That may be true, but I am looking at this in a 'would this be right for the boy right now' mindset.
I am not looking at it from a $$$ perspective.
He started with the DS80, which had a good engine for him but too small a frame (he's tall), went to the XR100 which has a larger frame but a more tame engine, so I think this might be a good transition to a 125.
Its a bike like you said, kids are racing at 15 years old. So it could be a decent first real dirtbike.
And if I can do it for cheap, then that is what I need right now. Plus, the XR100 is slow and he is way to tall and heavy for it anymore. He just went/is going through a major growth spurt, and he needs all new clothes.
Resale value is not on my radar for the RM right now; track time and experience is, and the price is right.
I'm sure he wont be on it long, he goes around the track as fast as I do these days.