This appears to have all the telltale signs of a PayPal scam. Here's how it works:
1. The seller will attempt to get you to send first and will steadfastly refuse to use any kind of escrow (or may attempt to get you to use Escrow.com and then spoof the Email in an attempt to get you to send to his own address). He will use the reasoning that you are protected by PayPal, and if he doesn't send you the coins you paid for, you can always dispute the charge to get your money back.
2. Once you send payment he will either disappear completely or stall for time. In this case, the OP has already baked in 1-3 days of time into the deal.
3. During this period the seller will move the funds out of the (stolen) PayPal account and convert it to cold hard cash in his pocket.
4. By the time he is supposed to send you BTC, he is long gone.