First of all,
WELCOME. Believe it or not, we are a friendly bunch (cmon guys, wheres the welcomes to new members?).
The site nice, however, you are aiming at a market that is quite simply saturated with 1000's of other people trying to launch an eBay rival. Also, as has already been mentioned, why should I choose your website over eBay?
I guess this question could also be asked of T4Tom4 - why should he advertise on your website? I appreciate it is fantastic and novel way of obtaining a link, but I want visitors for my money too
As for the amount of time it took to develop, well it depends if you are new to php or not. Even with templates, it can still be tricky to get things looking and feeling exactly how you want, and to get to grips with different CMS terminology.
Personally I would think about other areas to go into, and take this as a lesson or a learning curve.