Start Your Own Social Network?

How hard would it be these days to put together a simple "Start Your Own Social Network" software package?

The add-on market could be major. This would allow a low entry price for the starter package.

If the starter package were a groupware project, it could be delivered for free. Its authors could then go on to write add-ons as shareware and sell upgrades. Or sell the premium version independently.

Even attempting it would look good on the resume.