I can deploy 5 figures per month extra against the next crummy commercial loan I have over 6% if I want to, or invest elsewhere.

First and foremost, I need a great real estate agent who is able to provide stellar service and won't be turned off by individual smaller priced homes. 

No deals, no extra payments (because you haven't used the line).You only want to increase your debt in a primary residence in two cases. 1) You make more money than it costs you.

A lender will look at DSCR for a commercial loan, but as an individual investor I would never use your criteria.

One thing to note is that most DST’s are loaded with a ton of extra fees (sales commissions, etc), so they may not make such a great first option.

ARM loans, unless you pay a ton extra every month so that when it adjusts its not a shock, I would stay away. 

You will have to pay higher property tax and utilities and maintenance will go up a bit but the extra unit is well worth it because you'r essentially upgrading for free.You need to take into consideration the closing costs of selling your house, buying the 3 fam, and mortgage for the new house.

Currently the outstanding loan amount is $34,000 under the tax assessment so I can use the equity in future property investing.Yesterday an individual from a respected property group in the area stated the house would rent for $1,300 a month (which matches my research). 

But also @Linda D. makes an extremely good point, in the mean time, stay extremely engaged in surrounding yourself with like minded REI individuals as this will continually remind you and motivate you to stay accountable to your WHY you are doing this. 

Like if now they pay an average of $50 in electric but I get panels and say I'll cover electric for an extra $25, that is a $25 decrease for them and possibly covers the added cost to me which over time gets paid off and an added benefit for new renters going forward.