Check iScripts SocialWare. Its an opensource application. So you can modify it anyway you want in the future. it has a tiered subscription feature which allows you to create free and paid plans with different modules. Also got an activity points system which offers points points for different site activities. These points can be traded for virtual or real goodies in the gift store. The is stickiness feature to improve member participation.

You can create a social networking site off the script in minutes. Just upload the script to a hosting account, and install your script through the install wizard. You can customize the network from the admin panel. Best part is you are not locked down to a proprietary platform, if you have different plans for the future.

You don’t need to pay to have someone reinvent the wheel. There are plenty of open-source solutions. I would recommend Elgg.

Unless you are a highly-experienced professional web programmer (in which case, you wouldn’t be asking this), this is beyond your ability to program yourself. Look into some sort of portal / forum / cms solution.