I live in a cheaper market with a lot of sub-75k properties.

Yes, Builders have a lot of margin that they are working with typically because they set the market and manipulate the home prices.

It is not on the market but I have an investor who is interested in purchasing it. 

With the economy and market as they are, should I continue aggressively paying down the HELOC to potentially borrow against again or should I just pay the Interest Only (IO) payments and seek other funding at the current day higher interest rates?

You probably have heard to join the local REIG as what you will find from the courses advertised everywhere anymore is that they offer general information that in many cases does not fit your market or state requirements. 

The facebook groups are a great place to find mentor programs and such in your local markets 

New constructions in the neighborhood are selling for a significant amount above construction costs (double or more the market value of the land).  

Dba is typically for marketing purposes or if you are in another state and that name is already issued

This would significantly help my ability to afford the market from a house hack standpoint, but I want to understand what those tax advantages are renting out my basement as a business rental.

I would like to purchase a 2-2.5 mil home with the proceeds that will eventually be our primary, but that we could buy initially as a second home/investment and rent out for the remainder of 2024.