Collaboration Portal structure development

need an estimate of time/cost for below development need a basic looking collaboration portal with following features > expert can create a profile and post skills/time availability > users will query for skils/time/zone > system will tack transactions and feedback > electronic payment no particular requirement on technology used - ajax is a nice to have I have some computer skills so i will take care of contents + layout + graphics required is the site structure and database part requrements > Very Good English > Clean and easy to understand code > communicate via email or chat (google talk/skype)