As we all know, you are really paying for the commission in the purchase price. 

Is this LTV based on ARV or the purchase price? 

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.

I own a commercial unit, and I’m trying to determine a fair rental rate for the space.

Purchase price: $80,000 Cash invested: $145,000 Turning a 3/2 into a 4/2 duplex for short term rentals.

To defer all tax you must purchase in total at least as much as your net sale.

I have a followup question - I will realize a lot of capital gain from this home in Idaho, so I think unless I purchase a new primary residence I will have to pay that capital gains tax. 

The city where you invest determines all long-term income characteristics.

You are definitely going to want to get a lawyer and as soon as possible.This will sound harsh.In your story, you have made a number of very poor decisions about how you purchased and managed this property. 

Plan is to purchase a couple homes over the next year.