Book recommendations and websites are appreciated.

There are a few programs that can do second position financing but typically underwritten based on your personal income.

Mostly people with minimal RE experience are adding a single ADU and they often make that choice based on cash flow without taking into account the negative equity position.  

Private Lender Partnership: Partner with a private lender or investor willing to take a second lien position to get you to 85-90% cash out.

The 1st position loan is paid off but has a second position heloc on the home with 50k balance.

The land loan is in 1st position on title which would put the loan to build in 2nd position.

Recently, I sold my position in a company due to an acquisition, which liquidated $750,000.

I'd personally never take capital that I am paid to manage without committing my full-time effort to the situation and putting a majority (I reserve the right in the future to make this 1/3rd of my position) of my wealth into the situation. 

Positions with real estate investors or related roles can offer income and experience.

Quote from @Michael Challenger: I have no qualms with hard money lending, but I need to learn more about the process and structure to these for typical deals so that I am more comfortable and in a position to reduce my personal risk and risk to investors as much as possible.