Reached out by a startup

So I got reached out by a start up or more of a person who is trying to start one. We talked for a while and he stated that he does have a small team consisting of ex fanng engineers with a legal firm backing them. I do like the product and we planned to talk more later after I sign a Nda. But I wanna ask kind of how legit could this be and what should I look for or ask? I'm no one special and I haven't even been in my current job for one year so getting reached out too make this seem a bit far fetched. Any advice is appreciated.