This ==> "1. Hard-coding the income on Sch C."

1099-Misc has various boxes, so that clues you into their activities: business, landlord, royalty, etc. It is not the amount to enter, by itself. Let's imagine a landlord rents 25 storage units. Only 3 are rented to businesses, so only 3 tenants will send your taxpayer client a 1099-Misc for rent they paid from their business to your taxpayer client, the landlord. But your taxpayer client has rental income from all of their rental activities. That's what they provide to you so that you can prepare their tax filings.