I want to start a site like ebay. (not another one!) How should I proceed?

I am interested in opening an online store site like ebay in Brazil.
How much would it cost? (in dollars and if I were to hire an American designer?)
How long until i get a site up and running? (if I had a team of 3 working on it? / If i had some company work on it?)
How and where would I market the site?
Any interesting ideas on how much to charge on fees?

Lots of questions, just pick a few if you don`t feel like answering it all. Thanks