If you just want to help them out and are very familiar with the market, a great option and what I would recommend for them (given they have proper knowledge or guidance) is cash out refi, invest in a high cash flow area which would most likely not be Austin, then receive monthly income that way, It should be more than enough to cover the new mortgage as well as provide enough monthly income to live off of assuming that their monthly expenses are not too high. 

I'm not concerned about selling a home with a properly remediated sinkhole along with the appropriate engineering sign-off, my question is, does anyone know of an engineering firm or company that can further investigate the sinkhole to determine exactly where and how large?

How do you know they are getting the repairs done properly? 

I guess my question was not worded properly.

Many people don't properly run LLC, so they have an illusion of security more than actual security.My best advice is have good liability coverage limits on your insurance.

IE you cant make a loan on a primary residence without full dodd frank and license .Now there are a few lenders in the Los Angeles Market that are properly licensed to do these loans.. but very rare any where else.check out these lenders.Lima oneLending homevisio Civic Dominion for what you describe a 10% apr could be had as long as your credit is decent.  

Make sure to get professional guidance as transferring a property to an LLC can cause the acceleration clause to execute and require you to pay back the full mortgage.

You may end up having to stay in the property a little bit longer (for example you thought it would take a year, but it ends up taking 18 months to execute your plan) but you can absolutely do it.

Get a properly screened renter (thru a reputable property management company) who signs an annual rent agreement that pays you with ACH direct deposit monthly.

Vetting properly should reduce this risk but I'd at least want the security knowing that we're not tied to living with each other if there are issuesAside from these two questions I have for the builder, is there any other question you'd recommend I ask the builder?