We really, really don't want to waste valuable materials trying to assemble a rat cage, especially when it needs to be big enough to hold multiple rats. Imagine trying to build a canoe out of formerly usable circuit boards. Go to the junkyard, find materials for assembling a cage or cages. Anything vaguely boxlike that allows or can be modified to allow us to see inside will probably do, but we want our rats to have a fair amount of space to move around in. No good getting claustrophobic rats before we've even done anything to them.
On a related note, I approve fully of ratborgs, but also approve of leveling our skills before trying anything serious. I could understand trying to map a rat's brain, but even that isn't going to be useful until we're ready to begin production, and I think that'll take a while. In the meantime, we should focus on smaller projects to increase our skill and provide minor benefits, not make half-assed approximations of what we want to do eventually.
Finally, come on guys. A proper mad scientist doesn't murder hobos or get into shootouts with security personnel just so he can steal a goddamned stereo or perform amateur neurosurgery, and he certainly doesn't sell his precious robots to whoever will buy them because he's desperate for cash. If we need money, we need to make it properly. At the moment I'd say we should be more concerned with practicing our skills than acquiring funds, partially because skills make those funds easier to acquire. Scrapbots wouldn't sell for much anyway, but a quality spybot or high-powered drugs might.