How to Vet a hard money lender when investing my money

[Marina OLeary]

I am interested in investing with a hard money lending firm, as in investing my own money to fund deals through them. 
What steps should I take to vet this lending firm?
I've spoken with them, seen examples of previous deals, I understand how the business works, etc. I guess I am wondering what else I can do to verify that the lending firm is solid? 
To be clear, this is not to buy my own property. It is using my money to fund someone else's loan request through this hard money lending firm. 

Thanks!