But I would imagine the credit card companies would start to restrict me at some point.

This is bigger than most can imagine.

Hopefully someone with more tax knowledge than I will chime in, but as you can imagine, they are busy this time of year.  

Imagine what our grandparents paid for TVs relative to their income, for a 12" BW box inside a cabinet that weighed 300 pounds, especially in today dollars . .. . 

I can't speak to the other markets you listed but they are typically compared to our market here so I imagine they're similar.

It's flawed in every way imaginable.

Especially in vacation homes I imagine. 

Imagine buying a $7,500 roof every 6-8 years on your $50,000 house that collects $7,200/yr in rent.

You have to use a bank trust (fideicomiso) but it's like having the property in your own name for all intents and purposes.If you decide to buy and build, you'll have to do everything by yourself, although I imagine that the developer would be on hand to help you if needed.

I would imagine you're capped at 70% LTV to make the DSCR work at whatever threshold that lender allows (typically 1.00x) or maybe it's a credit/FICO issue. 3% in origination also doesn't seem too far off depending on the loan amount.