Crowdfunding - our commercial loans are syndicated through a series LLC with each series being a single loan.  

There is many sites online now happy to provide a tenant a FAKE paystub.

I literally think of loan sharks or getting your house or assets taken away from you when I hear it LOL. 

As a private lender would you pay the full 100%, or still do 75% Loan to Purchase price and have borrower put money in?

Are there other ways to invest idle LLC cash in online savings or money market funds? 

One of your biggest challenges will be separating all the online fluff from reality.EXAMPLE: several S8 "gurus" have already been exposed as frauds, but unfortunately, they sucked in thousands of investors.You're an engineer, use your education & experience to start building up a logical approach to investing in rentals:)Start with this:Recommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.So, when investing in areas they don’t really know, investors should research the different property Class submarkets.

I even got an email from a private lender offering a loan AND the collateral due to the borrower burning through capital and now they are stuck with it. 

I also have a primary residence with nearly a JUMBO loan at a high interest rate and I own a vacation place in cash (small trailer not worth much money but i also own the land) in a different state that I pay RE taxes on. 

Books, online resources, and local investment groups, etc.

If I’m going to use a combination of hard money and conventional (maybe FHA) loans, I will need a LLC for hard money eligibility anyways.