Website Redesign, CMS, Database (established website)

I am the owner of [login to view URL], a college subleasing website for students living off campus. The market for this service is simply too small. I would like to redesign the site and gear it towards the general public so everyone can list their space for lease or sublease. We are ranked page one on google for search terms such as sublease, college sublease, sublease agreement, etc... Obviously some SEO changes would need to be made to tweak it and gear it towards the general public. Here is what all I am looking to do. Most of this should be relatively easy as I am not looking for anything cutting edge. -I already like the design of the site but would prefer it functioned a little differently. [login to view URL] is a similar site that does what I would like for [login to view URL] to do. I prefer my layout but here is what I like about sublet.com. They currently allow people to post for free and search for free but here's the catch...If you post a free lease, only paid searchers can view it. If you pay to post your lease, everyone can view it. So, there are reasons for both the person posting and the person searching to have paid accounts. -I would like the site to automate payments so that listings will renew after xx months and re-charge the customer. If the account is not paid, it will automatically be delisted. -I would like for posters and searchers to have login access. This is something I do not currently have. Posters can view/edit their listing and searchers can bookmark listings they are interested in and have conversations with the posters of other listings. -Another big part of the redesign is the CMS. I want to be able to create content and add to the site as I see fit. I am fairly good at SEO so I know the value of adding content and keeping it fresh. -I currently only accept payments through paypal, which is fine. The only problem is that the customers have to actually be transferred off of my site to [login to view URL] in order to pay. I believe paypal offers the ability to process payments within my own website. If so, I would like to utilize this. Time is not really of the essence so I would like to pay less and allow you much more time to work on the project. Please provide some examples of your work. Thanks, Justin