To start, @Geren Knight III. 10% combined for Repairs and CapEx, probably isn't going to cut it.

Both of those homes were over 7,000 SF and they were a combination of stick build for the big open areas and modular units everywhere else.I would be happy to sell some of my designs but I would want to be sure that they work on a specific site.

At a minimum you need 750 hours spent on real estate you ownAnd you need to spend more time on REI than any other job/ combined activities 

But I have not seen anyone do that, ergo I must assume the market is too small for such things, that borrowers wouldn't be willing to pay such a fee, or perhaps it's against the rules, or some combination of those factors. 

Think of it from this stand point in a years time you'll have two homes worth combined ($180k + $120k) of $300k for just the cost of the increased mortgage amount of a few hundred dollars a month if you're not able to have the first home paid for by your renters. 

To me, it sounds like a rationalization combined with nothing more than a transfer of the problem. 

I think many on here will find the 50% rule is a combination of the 30% rule for people that get class a and b rentals and the people in the d grade properties averaging around 70% if not more. 

But if you're looking to grow the combination of the captured equity plus, large investment needed, and long time without profit might have you looking into the 1031 option like @Soh Tanaka did.

We have decided to combine our efforts and, well crush it!

Hopefully, that fact combined with our low DTI ratios and high credit scores will allow us to perform a refi in this difficult time.