Christopher is skilled at finding and purchasing properties at sub$-$market prices. He typically owns these properties for only a few months, making a few upgrades and then flipping them for a profit. Occasionally, he buys a property with a tenant already in residence and receives rent payments before selling the house.

How should this rental income be reported on Christopher's tax return?

Not$-$for$-$profit income, reported on Schedule $1($Form $1040),$ line $8$j$.$

Business earned income, reported on Schedule C$.$

Investment income, reported on Schedule D$.$

Passive income, reported on Schedule E$.$