In Search Of Small Kid's Bike

Hi! I am looking for a bike for a 3 year old.  My son has recently taken an interest in bikes. (Probably because his big sister is learning to ride.) I know nothing about bikes, but google says a 12" or 14" should be a good size for him. I'm not opposed to paying...just trying to avoid buying a brand new bike since he'll likely only get a year or 2 out of.  Hoping someone out there has one they're trying to get rid off. Thanks, Holly