This seems to answer my question as well, so thanks! But where do I enter the principal income? Also, I seem to have read something conflicting--or at least confusing to the layperson (me!) about dividing the principal in two portions on the return--one of which is tax-free? Perhaps this only the case if the contract is COMPLETED during the tax year in question? (mine will finish in 2020, so for 2019, I am JUST receiving monthly paments...) The following was taken (and likely misunderstood by me) from https://smallbusiness.chron.com/tax-filing-land-contract-irs-31798.html
Installment Sale
IRS Publication 537 defines an installment sale as the sale of property that results in at least one payment after the tax year in which the sale took place. If the seller treats the transactions of a land contract as an installment sale as defined by IRS Publication 537, the portion of the money received for the sale that is not interest may be divided into two sections. The first section is a tax-free return of the adjusted basis in the land subject to the land contract. Sellers can use the IRS form Adjusted Basis and Gross Profit Percentage Worksheet A of IRS Form 6252 to determine their adjusted cost basis and gross profit from the land contract. Sellers with installment sale income should complete and submit IRS Form 6252 when filing federal taxes for the year of sale and for two subsequent tax years.
