Since he lived there a long time he gets a $250000 exemption. That plus his cost basis brings his capital gains to about $175,000. The zero percent income bracket for a single filer ends at $41,675 and is 15% after that. But his cost basis includes not only what he paid for it but also capital improvements. He must have made improvements over the years—new roof , remodel, etc which expenses can be added to the cost basis. And of course the expenses of the sale, realtor’s commission, etc. would reduce the reportable proceeds. Remember the capital gains rate bracket reflects taxable income, not AGI, so his standard deduction also lowers his taxable income.
