I have a client (age 72, single) who makes less than $35,000 per year. He has 12-13 properties (most are rentals) that he bought in the 70s and 80s that he owns outright. He wants to start selling them off and has asked about the tax implications. I thought that his income was below the line and that he would be in the 0% bracket on capital gains tax. I've looked at the IRS rules and from what I can tell, he'd owe no capital gains. But when I set up a "dummy" return, where his capital gains are in the $350,000, he owes capital gains tax. Could you help me understand this?