Generally a T12 and prior two to three full years income and expenses (broken down by month) along with a current rent roll is enough. 

By the end of this assignment (I move again June 2021), I will have 3 properties netting ~$1700/mo.My question is, on my timeline I have another 14 years of active income to turn into passive income - should I start rolling my $1700/mo back into my mortgages to increase cash flow from rents, or should I focus all of my funds on acquiring new properties?

Is it possible to roll closing costs in the loan?

You can also get a 203(K) loan that rolls in rehab costs. 

Congrats on getting rolling in this business so early.

@Bob Green Hi Bob, I could probably take out a HELOC and I'm considering rolling over my 401k now to a self-managed IRA.

Many of the units are 50's and 60's models, and anything that old is going to put up a pretty heavy fight before those wheels will roll - and then you have to hope the axles don't start on fire after 2 miles.  

Google it and you'll find different ways of attaching, as it will have to allow the big pipe to still roll, when the dog touches the pipe. 

In that time, I've also built up over $200k in equity, so selling and realizing the gain and rolling into another investment is also an option.Again, the market has spiked a lot more in recent years.

I will be getting a rent roll and lease agreements to confirm, but assuming they haven't lied about the rental income then the purchase price I'm getting this property for pencil's out.