For Sole Proprietors The first link below opens a .pdf document that outlines the various income and expense categories that are reported on a Schedule C and discusses what record keeping is required. This document makes several references to the following companion Excel spreadsheets that can be downloaded and used to track your own income and expenses.
For Rental Income This link will take you to an excel spreadsheet that can help you track your rental income and expenses. The second tab will give you the instructions on how to use this tool.