I have a builder in San Antonio that offers a 4.75% interest rate on their duplex's.

I mention this as I have seen some people want to sue companies because they were a sponsored affiliate on a website…Regarding the original post- expect 10-12% (I think latest I saw is avg is 11.5%) rate plus atleast one point for a 12 month loan.Bigger companies may take longer for approval and can be more flexible usually in down payment amounts.

And keep in mind that the rate on the 2nd lien will likely be 10-12% so depending on the cash flow it might not actually yield that much cash to you at closingMore importantly, it's just more debt so ultimately it sounds like you need an income-producing event to actually improve your situation and avoid some of the consequences that you mentioned

What was the specific rate he was quoting you?  

They got fundamentally sound real estate, with matching debt (10+ yr fixed rate) and budgets with the intent to hold nearly forever. 

Cap Rates in the area.

go to Anthonys RE school take you a few months and your in business.

Most people make the mistake on putting to much moey down or use "All cash" and then need to pull it out later at a higher rate.

780 or higher should get you the best rates/terms available, no difference than 820 score.

Rental Demand and Rates: What is the current rental demand for ADUs in this neighborhood?