Get your taxes done using TurboTax

The cost basis, because it was a gift (not inherited after death) is the same cost basis as it was for your mother.  $30,000, plus any capital improvements after her purchase and before it was transferred to you.

You can enter your second home sale by following the instructions below.

As you go through the sale of your second home, there is a dropdown to select 'second home' (see the image below).  Also you likely did select the correct box to enter the sale after you select Stocks, Mutual Funds, Bonds, Other (1099-B), be sure you selected the 'Other' box. 

The second home sale can be entered into TurboTax CD or Desktop version by following the steps below.

1. Open your TurboTax account > Select the Personal tab then Personal Income > I'll choose what I want to work on
2. Scroll to Investment Income > Select Stocks, Mutual Funds, Bonds, Other > Start or Update
3. Add or Edit your sale that is NOT reported on a Form 1099-B > Select to enter a summary of each sale (you only have one)
4. Enter the Total Proceeds > Cost Basis (shown above)
5. Enter the holding period - if you owned the property for more than one year the it is long term, one year or less is short term
6. Continue to finish your sale.  

The gain from the sale will be fully taxable because a second home is not eligible for the home sale exclusion and it must have been your home. See the image below for assistance, the first one is for TurboTax CD/Download and the second one is for TurboTax Online. Whether you specifically select Second Home is not relevant for the tax return itself.