Here's my take on the questions you posed. As 
always you can take it or leave it for what it's 
worth.

1. When payment is received(i.e. money order, 
cashier's check or paypal), it should really only 
take three days to either send out the cel or 
explain why you need more time to do so. 

2. If they are willing to list some defects, but 
not others, it may be an honest mistake. I would 
look at the person's feedback or ask around about 
them if it is not an auction sale. Most cel 
collectors are more than welcome to tell you 
whether a seller is a plus or a minus.

3. Nice has nothing to do with business. A person 
can be nice all they want, and still screw you to 
the floor. It's happened to me and I'm sure 
several others on this forum. You send the dough, 
and they say, "Oh, sorry. The money hasn't 
arrived yet." Three weeks later you check and the 
money has been cashed. Then they say, "OK, I'll 
send it out tomorrow." Two weeks later, nothing. 
Then you hear, "The mail is really slow right now 
where I live. Should reach by the end of the 
week." And so on and so on. Reputation is what 
matters in selling. When you can honestly say 
that you have not had a single complaint in 
selling a cel, then that is a plus.

Hope this helped.