Thanks so much! I really appreciate all your help. When we ran the numbers, it turned out that redoing his 2023 or even 2022 tax would not actually make a difference—he just didn't make enough income to offset the loss.
The take home lesson is, take all the depreciation you are supposed to take when renting a property!
On the plus side, the final depreciation ended up being lower than his initial estimate based on past tax returns. Total rental time was lower than he remembered, 20% land cost needed to be excluded from basis, and the room for rent was only a fraction of the property. That combined with his low tax bracket meant that it only added about $200 to his taxes—better than the $2000+ we originally feared.
