Quote from @Caitlyn Frizzelle:

I’m looking for non-conventional lenders and posted on FB groups for recommendations/contacts.  I received  quite a few replies directly from lenders themselves.  How can I tell if a lender is legit? 

Also, if you have any you’ve worked with I the past, would appreciate recommendations! 

TIA

First, determine if the “lender” in question is an actual LENDER, or a mortgage BROKER. 
Mortgage brokers play a vital role in our industry - the good ones have access to financing options that borrowers don’t, they know how to package loans for the best chance of lender approval; they know which lenders are most likely to be interested in financing and at what terms; they can provide a realistic assessment of whether or not your desired interest rate, terms, etc are realistic.
In the non institutional money field you will pay 1-4 points in broker fees. This is in addition to the origination points you’ll pay to the actual lender - another2 -4 points. 

Going directly to a LENDER can save you the broker fees - or possibly cost you the opportunity for a “better” loan.  Especially if you don’t have a lot of experience.

Here’s a word of warning - most states do not require licensure for COMMERCIAL mortgage brokers, or mortgage brokers who specialize in business/investment purpose loans. As a result the quality of advice, service, and competence is all over the board. Besides the competent professionals, there are brokers who’ve never completed a deal and have little knowledge or experience; brokers who do nothing but resubmit loan requests to other brokers (daisychain) and brokers who disguise themselves as “lenders”. 

Best way to determine who is “real”
1- recommendation from someone you know
2- recommendation from experienced investor
3- check their website for professional presentation, etc.
4- check their references 
5- Google search 
6- criminal background check