I am in one of the higher tax brackets and could be saving around 40k~ a year on taxes with this.

Hey Jacob, do you plan on expanding the portfolio?

So advice to get the house against him and he will move out on his own is HIGHLY unlikely.  

He has used hard money as well as a line of credit from Chase for his homes.

You can simply request a separate check for the $100 increase to bring the total deposit in line with the new rent amount.

I've got about $525K in equity in the property, but lenders have told me that I cannot get a HELOC to access that equity for additional purchases because the duplex was financed as an investment - they have said TX law dictates that HELOC can only be used on primary residences.

Creative Financing" can mean a lot of different things depending on who you're talking with. 

(No mortgage on any).the cash flow is a total of $3,100 a monthDo portfolio loans exist for these kind of situations?

I know that interest on the acquisition loan can be included in the cost basis since it’s inventory.

Depends on if you have panels, crazy layouts, etc.