Hi,
Im just planing to develop a classified web site like Gumtree.

I have a lil bit idea of the process and Just not sure how to start the process..

Do I have to have a brainstorm for this or can I just start it like a ordinary web site?
I know I should have a plan if Im going to do it long term. Just need expert advise on this how to plan and start building the site.

Thanks