re: At what age is it appropriate to buy a kid a real four wheeler?

The Polaris website shows the youth Polaris Outlaw 50 to be rated for 6+ years old. Maybe because they don't think a kid can physically manage the machine any younger than that. Boys are usually a little bigger and stronger and may be able to handle it earlier.

I think you need to think about the "what ifs" in a situation like this. Nowadays, you put a 3.5 year old on a machine that the manufacturer says is for 6+ and she gets injured? I wouldn't be shocked to see an ER doc notify the authorities. Charge you with parental negligence or something.