JomSocial is the leading social networking component that is compatible with your Joomla powered website. Once installed, JomSocial needs to be configured by the website administrator and can be styled to match your site's design. JomSocial is a massive extension and there is a lot to learn how to set-up and run it, but the learning curve isn't bad and you can be up and running with your own customizable social networking community in a matter of days.
The JomSocial developers are very active and they have been releasing regular updates every 1-2 months.
The cost of (1) JomSocial license is $149 for the Professional edition and you can install, configure and set it up in approximately 10 hours with basic Joomla skills.
For full-service installation, basic set-up and testing, budget $500.00 USD. For full service installation, consulting, configuration, testing, training and live support... budget $2,500 - $5,000. Custom styling (CSS), integration and elaborate work flows are all possible with JomSocial.