Well, if you want cheap I hope you have a 4 channel radio lying around, otherwise start searching Ebay for a used futaba 4yf with receiver. Then you are going to need a camera and receiver. The usb receivers are tough to find but if this is gonna be in your house then you won't need usb. Just get one of the ones that hook up to a TV. They run anywhere from $80 to $110. The servos you can cheaply get, usually the cheapest are $10 to $15 apiece. They guys at linx motion have one camera mount with servos for about $36.
[link=http://www.lynxmotion.com/Category.aspx?CategoryID=61]Linxmotion.com[/link]
if you have the servos already then just order the pan/tilt assembly for $10. You can mod the pan servo yourself into a 360* servo by googling servo 360 mod. Thats pretty much it. But depending on what you have already to make one without having anything it will cost about $200 total for the intial setup. The good news is that the cameras by themselves are cheap, once you have the setup you can easily put one pretty much anywhere cheaply. It's the cam receiver and 4ch that are gonna hit the wallet.