Sticking with your Realtor's go-to LO means that you know you're going to get someone reasonably reliable and fast and a good communicator. 

Even have it in writing when I asked, so that would be interesting In writing will not matter, the Rocket LO was selling cars 6 months ago and just does not know any better. 

Quote from @Chris Lo: I did a hard credit pull with a lender (michigan) for the first time.With close to 100,000$ income, ~740 credit score, 10% down payment, First home buying, purchase price around 350,000$, and pre-approved for 400,000$.

There should be zero variation, but it seems not all LO's understand this.  

LO from Penny Mac said I would have to pay around 8 points for a conventional Investment loan.  

Also, have a competent LO that has a NMLS number (which means they can do dull doc AND DSCR, no NMLA means they can ONLY do DSCR loans) review your file to make sure you cannot go full doc.

I am not trying to scare you because I know some agents who do use their LO license on some deals. 

I know an LO using a competitive lead gen option. 

First you should become a MLO/LO before jumping into underwriting so you know the experience the MLO or LO goes through.

Your LO should go over this with you.