I think the rule on "owner occupied" rates is about it being a "primary residence," which is defined as your home for more than 183 days a year (ie, more than half of the 365 days in a year). The two out of five rule relates to whether you get the capital gains exclusion. You should be able to refinance once you are living there and get a better rate, but then again, rates will presumably rise in the next two years.
Rental properties typically require a bigger down payment and have higher rates to reflect the higher risk banks assume you represent. You should shoot for a 30% down payment. The other option would be for your parents to hold the note for you for a couple of years, or to get the mortgage on better terms and have you assume the loan. They could also guarantee it for you if you have trouble qualifying.