We are now in a position where we have 4 investment properties completely paid off making us money and I have a high paying W2 job that allows us to feel comfortable enough for him to quit his W2 job and start investing in real estate full time.So my question is… where can we go to get advice on how to move forward with this in regard to the best way to structure our growing real estate rental business?

I would also say there are even fewer "high end" 4 unit places in the metroplex.

Focus on quality, not quantity.

I highly recommend working with a real estate focused tax pro to explain your specific strategy, so you can be made aware of any pitfalls that could get you into trouble. 

In my opinion, you need to be able to estimate rehabs at least at a high level on your own.

I don’t think you’ll have a problem selling it as it will be highly desirable for either an investor or a home owner looking to house hack.

High interest for a short duration that you control seems like the way to go to me. 

Rents are all inclusive of high speed unlimited internet, lawn care, housekeeping of common areas, and all utilities.  

Because investing in real estate in general seems to offer more of an advantage than just stockpiling extra money from our W2 job into a high yield savings account. 

It's on the far NW side and has inventory in that price range, but consider that taxes are relatively high in Elgin VS most suburbs.