I'm 23, but I bought my first cel when I was 19.

I agree with the other statements-- the age of 
the collector doesn't really matter, as long as 
they *act* mature. ^_^ Whenever someone offers to 
sell a cel I'm interested in buying, I don't ask 
them "How old are you?" and refuse to do business 
with anyone under a certain age. Rather, I have a 
feel for them by their posts--- sometimes, by the 
comments on their webpage--- or, in the case of 
Ebay, by what others have put in their feedback. 
And it's a personal decision from there. If the 
cel is really nice, but I don't trust the 
individual, I'll pass, even if it's tough. And, 
yes, from various conversations in the past, 
there are a few isolated individuals who have 
very much lost my respect.

If you happen to be a younger collector, and are 
worried about the age requirement on Ebay, get a 
parent or an older friend to bid for you or sell 
for you. There's no shame in it, definitely... 
I've sold two items to moms who were buying them 
on behalf of their daughters. :o)

But as long as you have a record of being level, 
being mature, and being good to work with, I 
don't think anyone would have an age issue if you 
wanted to strike a deal with them. 

Take care,
-Cres