Besides borrowing money from 401k, you can open a line of credit on you Primary house and lenders can typically lend up to 90% CLTV or 70 investment properties.

So, some sort of reserve is needed to cover expenses.That being said, of course, at some time the water heater will need replacing. 

Assuming of course that your budget is ok with that approach...you'll have to run the numbers and see how long it takes to make back your investment, and if that is in line with your future plans....

A downfall of this process is the lack of tenant screening (background, credit, eviction checks) as far as I'm aware of.

Great for cash flow but of course depends on the property.

Am I to get all the credit?

I've been in a leadership course where the instructor described me as "Ready, Fire, Aim" right off the bat.

Account Closed, your forgot the folks with substance abuse problems and gambling addictions, and of course those who are really terrible landlords. 

I have a great credit score and solid W-2 earnings so I’m pretty sure I could assume the loan.

Based on their overall application (credit score, references' comments, etc.), I'm able to make a determination whether to rent to them or not.If they later move an ESA into the unit, they may be evicted based on the lie in their application, not on the fact that they have an ESA - but that's my take on the matter.