And the first thing speculators learn is to say "Yes, sir, I do" in response to that question.
I have, in the past, had a client (or should I say, POTENTIAL client) say they lived in a property or planned to live in a property that I soon discovered they had NO intention of occupying. If it’s a refinance it’s easiest to tell, things like the home address on a paystub or bank statement not matching, or the home in question is in a horrible neighborhood and another property they own is in a nice area, etc.
On a purchase it’s harder to tell, but there are clues that can often be confirmed by the way they answer questions.
If I suspect they’re lying, I call them on it. In a professional way of course. And then if my hunch is right I tell them either I do the loan as an investor loan or not at all.