I'm sure they have a lot of critics though.The average length of homeownership is nowhere near 30 or 40 years so most people never end up paying off their homes as a result.If your goal is cash flow today, then a 40 year loan with a 10 year IO period is about as good as you can get.If your goal is to have a paid off property in retirement, you should obviously lean towards a fully amortized loan on as short of a term as possible.

Is there anything critical to focus on or consider?

Examples to the contrary, I just cannot imagine a scenario where my inability to get critical resources would outstrip my existing stock on hand.

Notice is critical.2. 

That’s why creating a Inspection Checklist is a critical part of moving in.

It becomes a representation made by a borrower.Lenders have read the book, they know where the fudge is, they can see through embellishments, especially in RE valuations unless an appraisal is supporting claims, and it's rarely critical to see equity in other properties, if it gets to that point, it's not a very strong application.Your best approach is not to dress up statements.

No bad areas.I know this seems counterintuitive but it's critical as tons of these props maybe 90% are in bad areas.

Let's use the quote I pasted above as my case in point.EDIT: I had posted a long criticism of the math you posted above, but in retrospect, criticizing what you wrote above insinuates that I think you just made an honest mistake.

So, I don't want to feel like I'm using someone.I'm getting married in February, and while I have the full support of Future Wifey, I know that we have to keep all of this secret from her family because they are too judgmental and critical and any conversation with them ends in, "You shouldn't do that," and "why didn't you do this," etc., even when I know they have absolutely no idea what they're talking about. 

Ok, I just went thru the exercise with hubby, asking him the same question you asked me :)It looks like the most critical thing we don't have but you do, is a very reliable handyman, as well as housekeeper.