Where do I enter income from sale of second house

[Carl]

You don't "enter the income" per-se. You report the sale, and you'll be taxed on the taxable gain from that sale. Report this sale under the Personal Income tab in the Investment Income section. Elect to start/update "Stocks, Bonds, Mutual Funds, Other" under that heading. For "Did you sell any investments in 2016?" click the YES button.

For "Did you get a 1099-B?" click the NO button.

For "Choose type of investment you sold" select "second home", click Continue, and you should be able to take it from there.