Vetting Private lenders

[Kevin Benjamin]

This question relates to private lenders who may advertise in Facebook groups.

What are some keys to determining if they are legitimate?

I've been in contact with these two, for example, and was wondering if anyone has had any experience with them:

https://www.arcadelenders.com/

https://www.stratacapitalfundingllc.com

(Sorry if this is a redundant question, or if information on this topic is available somewhere in BiggerPockets.)