Vetting corporate private lenders and brokers

[Maribel Manibo]

There's a ton of FB groups where people claim to be a lender but turns out they are not individual private lenders or are part of a "network", which is fine. Would like to know how you tell if they are legit, especially the brokers. What steps do you take to check them out? What are red flags? Are there ones to stay away from... etc? Has anyone had any bad/non ideal experiences and what lessons did you learn and what would you have done differently?