Partnerships are very difficult and the more people you have involved the more complicated things can get.

To manage a property is not that complicated.

It's not really that complicated to buy out of state.

Business would be important starting out but eventually you’ll probably hire out the more complicated business aspect (legal/accounting).

For duplex, the rules are a bit complicated for owner occupied. 

But the latter can just be complicating things unnecessarily, but a benefit is if you do think you will co-invest with folks other than your father.

If the latter, that complicates things.

C Corp's double taxation rules definitely makes things complicated. 

But -- there may be structural planning opportunity there if they are C Corps.At a high level, you're creating a lot of nexus and potential filing obligations by buying each new property in a new US state.Your situation is complicated enough to warrant long-term, professional advisors.You'll need to consider not only your US income tax exposure and obligations, along with which tax elections and tax entity structuring is most favorable, but also your US estate tax exposure and your tax obligations in your resident country relating to the US situs assets and income. 

But, it could be a little complicated for a smaller building like duplex/triplex.