HELP Needed

Hello

I am just about start a Internet business with a very tight budget.!

The features I would like to have in the website are the following
1) Login and profile area for my clients
2) Option for the clients to list something on to the website.. something like Gumtree
3) Paypal integration to take payment when they list something on the website.

One of the examples I really liked is http://www.kickstarter.com. I would like to create something with a similar structure.

Thanks in advance