I sold a second home I owed for 9 years. Not really rented just put my family members in from time to time. I never earned money with it. I made 120 thousand on the sale.

[fredkozic]

How do I file?

[DoninGA]

The second home would be reported as an investment sale.

To enter an investment sale -

Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Under Investment Income
On Stocks, Cryptocurrency, Mutual Funds, Bonds, Other (1099-B), click the start or update button

Or enter investment sales in the Search box located in the upper right of the program screen. Click on Jump to investment sales

[fredkozic]

I paid 30000 in principle payments over those years. Should I post that as cost of investment?

[DoninGA]

No, mortgage payments, principle or interest, are not included in calculating the gain or loss on the sale.

Gain or Loss - Sales Price minus Sales Expenses minus Adjusted Basis (Purchase price plus the cost of any improvements prior to the sale).

[Hal_Al]

@DoninGA  said "The second home would be reported as an investment sale"

That is true in this case, as the property was sold for a gain.  That gain is eligible for the favorable long term capital gains tax rates.

However, that is not true, if the home was sold at a loss.  A 2nd home is personal use property. Letting family use it is still "personal use".  You may not a claim a capital loss on the sale of personal use property.