Additionally, negotiating with buyers directly demands a level of expertise and emotional detachment that might be difficult for homeowners with strong connections to their property.

.#1 Not super easy to find the discounted properties. 

If in your contract with the builder you made it conditional on inspections (including a radon inspection) and completed the inspection within the due diligence time period, I would think you should be able to back out of the contract without paying any additional costs.

For mortgage debt, the following additional requirements must be met:the party making the payments is obligated on the mortgage debt,there are no delinquencies in the most recent 12 months, andthe borrower is not using rental income from the applicable property to qualify.

When you need the work (usually because you aren't as good) you do it for a discount. 

You say they are trying to negotiate so it sounds like they are trying to get a discount. 

These are professionals with additional training and a stricter code of ethics.

In a few years you can use the built up equity to purchase additional properties. 

Due to the amount of liquidity you have, it's hard to recommend the SBL loan (or any additional leverage) without knowing your full financial picture since it does seem very risky.Now if you truly do have a home run deal in the works and it would cash flow and work with DSCR rates and terms (which I believe are only a couple points above most margin rates or conventional loan rates now), I would say that might be an option to consider.

You already discounted that while making the offer right?