I know you aren't supposed to use an "old" crib, but we are going to use one that is 16 years old - It went through both of my step-daughters and both of their cousins. I checked it out pretty thoroughly. It was a really nice one and seems really sturdy. I did decide to chuck the mattress and get a new one - ours had been stored in our basement and I was worried about the mold, etc.... Plus, I wouldn't mind using a used bedframe for myself, but wouldn't want to sleep on a used mattress, so...
I know there is a place on the internet to check what the current crib safety standards are (b/c I looked at it when considering this crib), but I can't remember what is is... I know some of the standards were that the slats should be very secure and should be no more than 2 3/8" apart (you shouldn't be able to put a soda can between them), they shouldn't have any posts that stick up that the baby could get caught on (when standing) and they need to have at least 2 positions, so you can lower it when the baby is standing. Also the mattress should fit snugly in the crib (you shouldn't be able to fit more than 2 fingers between the mattress and sides.).
edd November 3. (girl)