When I moved here 15 years ago, you didn't even cross over to the east side of the tracks. 

If we're both co-signers on 2 loans, does that count for each of us as two out of our maximum (10)?

I foresee one potential issue with this strategy but I'll also give your a solution to it.The issue I see is that a lot of conventional financing, if that is what you use on the rentals, requires 6-12 months of rent seasoning before they will count the rent as income.  

The upside of this is greater flexibility for the borrower and for those that want that level of far reaching capability while the downside of taking on this greater risk is that our rates will not be like an internet lender operating out of a cubicle.Fannie & Freddie have gone back and forth as to what constitutes a "financed property," but one interesting fact that I've field tested is that if a property is owned in a LLC and the debt or note is secured by your LLC then it does not count in the 10 or 6 count above.

@Dylan Cross You have option to take rehab loan or HELOC.

Duplexes 3 roofs possible 3 different locations.Room/ bath count?

There's ways to come with no money down such as using HELOC funds from a primary residence and doing a cross collateral loan. 

Another perk with non-recourse is, that so long as your insurance and taxes are in an entity's name, you will NOT have to count that property towards DTI constraints on Conventional loans underwritten with Freddie Mac.

It really depends on how comfortable you are with the operator and their plan - because if you do this type of investing in an asset where the cash flow does not cover the interest payment, you are counting on appreciation rather than cash flow and I never want to count on appreciation.This strategy can effectively create money from nothing - you borrow to invest in an asset, pay the loan and interest back and you either have cash or the asset and you have no skin in the game. 

I now want to purchase another investment property (3rd property) in a more affordable market with a partner and assume that the primary residence will count against my DTI.