There are a lot of factors like personal choices and goals that would play a role in which entity you might want to go with.

Would something you see on social media be enough to question their integrity?

You can get into 4-plex territory in landlord friendly markets for what you are planning on spending on a TH4) I notice that one of your concerns is 'enough time to manage'... have you factored PM expenses into your calcs in case you want to pass management off?

They will be a major determining factor in the success or failure of your investment.

This self-torture is not recommended.To make it more complicated still, other factors may come into play such as prior suspended losses from this property or other investments or maybe (albeit not very likely) the net investment income tax surcharge.

Lots of potential sources: other investors, family / friends, personal loans (I've used SoFi & Discover in the past, they loan in the $35-50k range depending on your credit), 401k loan, margin account against stocks you own...Just make sure to factor in those payments in the overall numbers.

The decision on where to invest comes down to a lot of factors including your budget and investment criteria, so it's hard to recommend specific areas.

I understand the factors driving it are different that the last Phoenix bubble, but are these prices sustainable over the long haul? 

. $12k, plus an annual bonus that averages to roughly $1k/month (if that can be factored in)Current monthly debts (including mortgage, property tax, insurance, car, child support): approx. $3.5kDebt-to-income concerns:Time for some napkin math for a concern that makes me worry whether this goal is actually possible...Assuming all goes as planned, I worry about eventually hitting a wall where I'm unable to qualify for new mortgages at a certain point due to how the investment properties' mortgages will affect my debt-to-income ratio. 

You can call and email from the software, process payments, send leases, integrate with an online resident portal, track renters insurance, receive maintenance requests,  and the list goes on.