Hope you have fun with your new ferret!
Ferrets do better when they have other ferrets to play with. If you only get one, he'll need lots of attention. As for a cage, here is a picture of mine. I've had one ferret in it and want to put a second one in there, but might decide they need something bigger. They need to have room to play; a rabbit cage would not be big enough. The best cages have multiple levels.
Everything can get pretty expensive, so maybe it would be better to earn a bit more money so you can afford a big enough cage and still get two ferrets.