I have actually done my own taxes in the past and plan to do so until it is too time consuming or too complicated (my BS is in ACC&FIN even though I do nothing with it other than personal stuff). 

Real estate investing is not suppose to be complicated. 

It’s a bit complicated because I have my my mom and two sisters as well on board.

You could certainly pay off the mortgage, before the foreclosure, and have your fiancé's sister sign the property over to you, but once it reaches the bank's hands, things become far more complicated. 

It seems like it is complicated or is it that I'm just trying to learn the Accounting side of it all.

I have considered going with a sub-metering service, but I think I will wait on that until I own more of the properties on that block or I can get the other owners to do the same.If you try to split a bill with your tenant you will end up having some complications with your tenant.Best of Luck

If a community property state, you'll oribably need both spouses to sign which might complicate.

It gets more complicated when cash is injected in the purchase of that note, there is now a cash amount advanced toward that sale price, the seller of that note agrees to accept X amount for the equity represented.

I would buy it from the HOA and deal with.... or it not, depending on complications and costs.

I should still be eligible for the credit for a partial year at least, (it's a primary residence with partial year tenant agreement) but breaking it down may not be worth the pain/complication of filing since it's less than $50.