Advice on building a multi-user website

I need consulting on what platform to build a website on. The idea of the website is to let (Finnish) music writers, especially lyrics writers and melody writers to find each other for possible cooperation. It is intended for professionals and freelancers with a professional approach. Therefore the site must have the possibility for participants to upload their text documents and MP3's or other data for review. Later, the same platform may be used to for other similar projects. Some special demands are: - different levels for visitors: Professionals, Hobbyists, Paid and Free - possibility for visitors to upload their text documents and MP3's - several users to control/monitor the website - as easy as possible interface for the "webmasters" as no one has experience with stuff like that - platform should need minimal upgrading or other maintenance jobs - if possible, the user interface in Finnish - free and generic tools are preferred - advice on if I can do it by myself with basic internet skills (I have learned to use Google Sites, a bit of WordPress and Blogger) - alternatively advice on how to get the job done using crowdsourcing with small costs would be nice I excpect the consultant to have experience on the tools recommended. What I need is simply "I surely know how you will get the job done and here's how".