What would it take to make a?

Social Networking Sites ?

We dont need another one

They're just like any other site. Unless you want to make something to rival Facebook, in which case good luck.

There's open source and commercial software out there that can do it. I've used SocialEngine for a couple of projects. It's a decent piece of software written in the Zend Framework, worth a look.

Like $50 and a weekend.

You really don't need to make a social networking website.

1.) It would be filled with your shitty mota spam
2.) It would look horrible, like your last website did
3.) No one would go on it, because you could never get it to be more popular than Facebook or Twitter unless you had some revolutionary new idea or a ton of innovation, which I'm betting you don't.