Research the area you plan to invest, learn what the most common expences come up and how often, apply a little common sense (add extra to the budget for the unexpected), and build a cash reserve or contingency plan to address these expenses. 

The ones that last usually made the decision intentionally, modeled it upfront, and chose operators who already had the systems in place.Self-managed or outsourced, the common thread I see in successful STRs is the same... the operation works before anyone starts optimizing.

I’m only touching the tip of the iceberg here, but beyond commonly known items like FBAR reporting, there are forms such as Form 3520 (and many others) that foreign investors need to be aware of, along with additional reporting, withholding, and structuring considerations.

I'm curious to know if this type of loans are even realistic or common.

Things in your tax filing need to be really off to do this.Being a REP/active participant and using cost seg to offset a spouses (or your own if that's all you do) W-2 wages is fairly common practice.

So, if a property appraises as is at 300k but being purchased from an estate as a common example at 230k.

That’s a common hurdle.

If that one unit has average stays of 7 days or less and you materially participate in managing it, that activity can be non-passive even though the rest of the fourplex is long-term rental and remains passive.Material participation is still required, so you’d be looking at the standard §469 tests, most commonly the 100-hour test where no one else spends more time than you.One thing to be careful about is allocation.

Common problem with section-8.

Your arithmetic is fine.Where people get burned is this part: the cap rate you pick must match how the market defines NOI, and must match the risk and class of the asset you are actually buying.Two common mismatches in your NOI:A.