Help to build a classified ads website

I am looking to build a website that is based on a classified ads webpage and makes it's money from selling advertising space. I am not technically minded whatsoever so have all the ideas and will be the sales and marketing person behind the venture. I need someone to discuss these ideas with me and make them real. I need a website designed where people can upload items for sale in the local area and can profit from this website by selling advertising space. Need someone who can help with all areas and help me to maintain the site by adding the adverts as and when needed so this is an ongoing project. A quote for the initial design would be helpful and then a quote for maybe each advert designed and maintaining the site. As much info in your quote as possible please.