Am I limited to buying a car in the ZH area or can I purchase from other cantons?

I see no reason why you could not buy from another canton. Just register it in ZH.

you can buy from anywhere. The car is only "from" a canton when it's registered.

I'm on a B. I bought my car at a dealer in Schwyz. They took care of the registration for me, which they did in Zurich. So my car came with ZH plates.

As said, you can buy a car where ever you like, just register it in you Canton.

the only thing you have to consider: if you buy a used car from a dealer in some other canton, make sure the MFK isn't older than a year - otherwise you'll have to get the car checked the instant you register it in Zurich.

I bought a new car from Aathal (ZH) when I was on an L permit. I had no problems at all, just the hassle of driving from Attalens (Near Vevey) to the far side of Zürich to make the purchase and collect it.

This means you can buy my car in canton Schaffhausen if you'd like
(see my thread on the 'for sale' forum)

Thanks for the info. Well, I guess it isn't so bad having a B permit and being a foreigner after all