From schedule E instructions: Whether or not you can deduct expenses for the unit depends on whether or not you used the unit as a home in 2018. You used the unit as a home if your personal use of the unit was more than the greater of: 14 days
or 10% of the total days it was rented to others at a fair rental price.
Client put condo up for rent in August, spent 4 days at the rental for a vacation but it was only rented for 3 days at fair rental value from 2/29/18 through end of year.
Client did not use it for more than 14 days. 10% of rental days is 72 hours = 7.2 hours. Because client used home for more than 10% of the total rental days, he cannot deduct expenses but also does not have to claim income. I think I got it right but brain is "overtaxed".