I was wondering if showing sufficient cash reserves in index funds can work for proof (even though I don't intend on using this money)? 

And since you're not aware of the process for HML's, I would respectfully suggest you first get all the education possible on the areas where you're not yet sufficiently versed.

Much safer places to put my $$ investment wise, where I can still sleep at night  

Their future home is not going to be available until then, they would be sleeping in a hotel, so the closing time frame was incredibly important to them.

I sleep in my own bed maybe 50 nights a year.

The mindless hours of Netflix, the boring dates, the unnecessary social obligations, sleeping in after late nights out, endless small talk, etc... all take away from doing things that add value to your present and future self. 

The one-liner mentioned above should be sufficient.

@Justin Holley if the uncle won't do the deal without the relative being involved then he isn't sufficiently motivated in the first place for a subject to.

I play in small ($500K to $1M) investments with my partners, and I find NC LLC structures necessary and sufficient.

I would not choose my leverage view if it was costing me sleep at night or other wise significantly impacting my quality of life.