Wordpress development for start-up C2C marketplace

Hi there,

I am currently starting up a company that will have a consumer-to-consumer marketplace as its trading platform. I have been looking at my options in terms of platforms and have found a wordpress theme that, with some alterations, may be able to do what I want. I am looking to get an approximate quote for the work. It would involve taking the theme at this link http://sitemile.com/products/walleto-wordpress-marketplace-theme/ and giving it the functionality of this site http://www.idonowidont.com/ (different design and product set but identical functionality and general infrastructure).

I am also open to alternative development options that the one listed here.

Many thanks.