My client needs a site customers can use to pay the membership fees and join. It should also track when old members need to pay again. There are some members that will not want to pay online and they want to be able to use the site to manage all payments. The CMS must be cheap to host online, potentially with something like GitHub/Heroku.

I am experienced with PHP and RoR. I am using a CMS so once I am done with this project it is easy for them to update.

After reading through different posts I think WordPress with an e-commerce Plugin may be the right solution. Spree and WebGUI also looks promising. Thanks for the help.