I already own numerous properties so, just playing worse case scenario/devil's advocate, I am assuming that after re-financing the 5th or 6th home, the income requirements will be significant.

I've used a HELOC on my primary residence numerous times to support cash offers/acquisition without messing with more cumbersome financing or partners.

The federal government and state of Colorado have numerous rules and laws to protect tenants and home buyers from being discriminated against.Here's a description of the Fair Housing Act from HUD's website: "...as amended, prohibits discrimination in the sale, rental, and financing of dwellings, and in other housing-related transactions, based on race, color, national origin, religion, sex, familial status (including children under the age of 18 living with parents or legal custodians, pregnant women, and people securing custody of children under the age of 18), and disability."

Craigslist originally, hard to find on the MLS due to listing errors.

In my local market there are numerous 3% down conventional products for single family, 5% down conventional products for duplex, down payment assistance on more than 1 unit properties, tax credits, all kinds of programs that have other ways to benefit owner occupant buyers. 

So while there's a lap pool, gym, concierge, bocce court, and numerous other amenities, there's nary a tub in the place. . . unless you count the tubs in the dog spa.

To continue from my response on #1, you can't afford to making a legal error that ends up in litigation.   

This is a 10-20 year play for me, so will take some trial and error to figure out the balance. 

The truth is, you could read 100 books and still not know enough because certain things need to be learned through trial-and-error.

One PMI company's software gives pricing, but if you call them the rep says it's a software error and points the finger at Freddie.Not actually clear on what is going on 20 levels above me.