A lender doesn't need to have an NMLS license but it can be helpful if the person has one. A lender who has an NMLS license will want to keep it and not be looking to behave in a way that could lead to having it revoked. Also, it will track consumer complaints that are registered. It can be found online at the NMLS Consumer Access website. 

An NMLS license is needed to do owner occupy loans and not loans considered business purpose such as DSCR or commercial loans. Working with a licensed person who has at least one state license shows that the person passed a challenging test, the NMLS test, that more than half of people fail on their first try. So even if it's not needed for the type of loan if business purpose / an investment property loan, it can potentially indicate a level of education and professionalism that not all mortgage brokers and lenders have.

 @Antonio Macias

Check for reviews, licensing, and have term sheets disclosing all lender fees in writing.Make sure the lender is held accountable for what they tell you can be done. 

I prefer having communication via text/email as this holds both me and the client accountable for any mis information or mis representation of terms/valuable information needed for secure financing.