I work for a bank, you can definitely buy a house on temporary visas like 489. However, not all banks accepts temp visa and therefore you don't have the option of shopping for better interest rate. As far I know only two banks accept 489 visa and each of their policy is different to one another, better discuss with a mortgage broker. Also, you need to get FIRB approval (I don't know how much it cost but I heard $7k - $10k). Temp visa holders are not entitled to FHOG (better check with a broker because even FGOG is different state to state).
Hope I answered you question.