I'm on the road three weeks a month. Does that break the live-in part?

The 51 percent of nights thing is forum folklore as far as I can tell. What you actually sign is an occupancy certification saying you'll occupy the property as your principal residence and move in within some window after closing, usually 60 days, and stay for a set period. Principal residence is about it being your one home base, so driver's license, mail, voter registration, tax filings all pointing at that address. A traveling salesperson with no other house is a different picture from someone who owns a place in another state and stays at the duplex on weekends. Ask your loan officer to show you the actual certification language before you get to the table.

Practical wrinkle on top of that: if you're gone three weeks out of four, decide now who handles a burst pipe at 2am. Onsite ownership is most of the appeal on a small building and you won't have it. I'd want a plumber and an electrician who'll take a call from a number they recognize, plus a neighbor tenant who has permission to shut the main off, before I'd close on this.

The part I got wrong for months was thinking occupancy was something the lender checks up on later like a home inspection. It's a statement you make, and misstating it on purpose is the problem, not being out of town. Which is why I'd want your answer in writing from the lender rather than from us.