In the end I think our income was high enough and the old mortgage low enough that we would have qualified anyway, so we didn't exactly get to test this in practice.

If you were to go back in time with all the real estate/investing knowledge you have now... what would you put on your checklist of things to do before getting started?

The best practice would be to cash out refi to reinvest the equity, or to 1031 exchange once your equity has built up.

Valuation is the cornerstone of my investment practice - both professionally and personally. 

Watch some of the BP videos or read some of the articles on how to analyze deals and start practicing on some in your area.

Yes, at first it is information overload, but just keep learning and practice analyzing deals.

I know these aren't the best for finding deals - but I have been practicing analyzing them. 

And then put in time taking practice exams and take them over and over and over until you feel you're continually doing well and you should be fine with the state test.BTW, when I was taking the state exam (WA), I was pleasantly surprised to see on it one of the exact same test questions from 360Training.

In the unit next door, one of the tenants was already practically living with her boyfriend and was willing to break the lease early, paid for all of March and actually moved out in early March giving me the chance to do some minor upgrades, have showings right away and get it rented to limit vacancy.

You need to understand how to use it on a daily basis: proper resolutions, annual meetings, banking accounts and accounting practice.