To enter your 1099-S or Sale of Home in TurboTax:

1. Open your return.
2. Enter "sale of home" in the Search box (upper right of the program screen).  
3. Click on "Jump to sale of home" link.
4. Answer screen prompts.

Sorry I realized immediately I wasn’t very clear. I meant a purchase price tied to the mortgage interest deduction. I assume it’s used to determine eligibility. 

When you are entering your 1098 (Mortgage Interest Statement) into TurboTax, you will be asked a series of questions, including your Outstanding mortgage Principal as of 1/1/2019.  

Follow these steps while in TurboTax:

1. Select Search in the top right hand corner of your screen,
2. Enter 1098,
3. Select Jump to 1098,
4. Answer the questions in this section.