The IRS does not reference principal or interest regarding the home. They want either the rent amount or the fair rental value of the home.
6. Lodging (complete line 6a or 6b):
a. Enter the total rent paid ................................................................................................................................................... 6a. __________
b. Enter the fair rental value of the home. If the person you supported owned the home, also include this amount in
line 21................................................................................................................................................................................... 6b. __________
7. Enter the total food expenses................................................................................................................................................. 7. ___________
8. Enter the total amount of utilities (heat, light, water, etc. not included in line 6a or 6b)....................................................... 8. ___________
9. Enter the total amount of repairs (not included in line 6a or 6b).......................................................................................... 9. ___________
10. Enter the total of other expenses. Don’t include expenses of maintaining the home, such as mortgage interest, real
estate taxes, and insurance................................................................................................................................................... 10. ___________
11. Add lines 6a through 10. These are the total household expenses........................................................................................
https://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
