First off Welcome too DRN..
I have heard nothing bad about the 03YZ125.. WHat is your experience w/motorcycles?? They do require some basic maintenance, such as cleaning air filters, chain adjustment and piston & ring replacement when needed.. Also what type of riding do you plan on doing?? From experience, it is kinda hard too "putt" along w/the kids on a 2 stroke MX'r.. But not impossible.. Also, you may want too check out the "CR,KX, YZ, RM" forum, may find some infor on a 03yz125..
Hope this helps you out,
Rick