Right. The big one is rent and houses; always USD *priced* afaict (though presumably you can pay in pesos). For big ticket consumer goods you might occasionally be able to pay with USD (also tourist things like taxis) but otherwise yeah you basically have to price in, and use, ARS which is not great. 

 Not a lot of currency exchanges around either, at least that I've seen so far; in Ukraine you can find a currency exchange booth literally every few hundred meters. 

 Calle Florida (off Av. Córdoba) is a big concentration but I think there's a broad shopping  area of the city around there where you find them here and there.