I intend on managing the property myself under the LLC, but want to ensure I dot my I's and cross my T's by hiring an accountant.

What would be some ways of ensuring a broker or realtor is investor friendly?

Their agent did them a disservice or they all knew what was going to happen (looking for the 1 in a million buyer, not caring about the data or neighborhood to put up that kind of money) just to "test it"So ask yourself this question...are you testing, or are you selling? 

Im in houston texas and would like to know what performance metrics should I seek in a 1 to 4 unit home to ensure Ill get approved for another loan year after year?

Basically any credit driven data on consumers is 'gold'.

We also need to make sure there aren't too many new apartments being built, so we look at those numbers as well.We get all of that data the hard way.

It also has free data and free sales comps.

This is a smallish town (pop 10k) but it is home too many large employers as well as Googles second largest data center in the world!

  :) Below is a screenshot of monthly revenue in a particular market I invest in from Airdna's data. 

First, ensure your credit score is up to par to receive your pre approval.