Just make sure they're not the only lender you speak to and get the proposed terms in writing before you commit to them wholeheartedly.

I am committed to buying a small multifamily property (duplex or triplex) in/around St.

don't commit until you know what you are getting into and what you can afford.

Let that lender know that you need their commitment on meeting the deliverables. 

What's to say he won't commit another felony...

Actually I got an offer for 4.5% interest but requires 1% upfront application fee (refundable at closing) 1% commitment fee (refundable at closing) How do I verify if it is legit?

The wholesaler probably just wanted to get a deeper level of commitment than the verbal. 

They can still buy a car, they still have their credit cards, they can still rent a home / apartment (or move in with someone else) - so the binding effect of committing to a mortgage just is not there any longer.  

Otherwise, you have to look at your other commitments, and how much bandwidth you have for this stuff. 

It is key that you let everyone in your current network know what you are doing and that you are an agent.Honestly from a time commitment standpoint your start to the career will be generating leads.