This is not including any financing costs and closing cost which can easily bump that number to 23k. 

How did you finance this deal?

Quote from @Guillermo Perez: Does anyone have experience with seller finance?

Through the LLC structure it is possible to take advantage of the existing mortgages modified first at 4,125% 22yers and 1%, yes one percent, for 40 years.

Look at photos, and look for homes that look as similar to yours as possible, in quality, condition, style and size.  

Each property qualifies on its own economic merits (i.e. rental income covering PITI payments)This is one of the main advantages for DSCR financing, i.e. the ability to scale without any kind of DTI limit imposed by conventional financing.

I worked with a travel nurse who does shift work and 5 lenders said that they couldn’t finance her primary residence purchase and I ended up making it happen for her. 

If you have an IRA LLC the custodian is not involved in the IRA obtaining financing including a refi.

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.

Another possibility is looking into a home equity line of credit (HELOC) on your personal residence, which could help you tap into available equity without a large lump-sum repayment upfront.