Their markets just didn’t understand the risk and either wouldn’t quote it at all or had really high premiums and inferior policy terms.

I suggest your respective LLCs be the members of the JV LLC, but check with a lawyer - maybe there're legal reasons to own the new LLC under your personal names rather than under your LLCs.Transparency is easy with a joint bank account.

If you use square trim you could stand the sheets of drywall up vertically, fire tape joints with self adhesive fire tape and cover joints with a 1" X 10" or 12" board similar to trim. 

I'm not a registered lender so max I could charge is 10%, so the risks are definitely not worth the reward, but maybe we could do a joint venture or figure out a way for me to get paid?   

My story of finding dirty birthday balloons and a joint in the crack of the couch doesn't really compare to that for this year...thankfully I guess. ;)Cheers to you and best of luck! 

Sometimes it simply creates a weakness at the joints, which leaks later. 

. * [Not a habit you'd want to continue].Might going into a joint-venture with a developer (who'd build on the lots) help?

I would use the money to Joint Venture with someone and actually learn how to do the whole process and own some real estate.

Typically an ADU is inferior in size to the main improvements.

Explore all options including an outright sale and joint ventures.