Let's start with a traditional underwriting list for income: last two years of Federally filed Tax Returns and supporting documents. (W2 forms,) If applicable: 1099's, K1's. business returns, and any retirement income documentation. Plus most recent pay stubs or if self-employed: a profit and loss with balance sheets from the last filed tax returns.
For assets we need the all pages of the last three months of financial institution prepared statements. This will be evaluated for source of funds, cash flow, expenses not documented on the credit report, and income consistency . All deposits will need to be sourced. Pay stubs are the most common source of deposit, but self employed borrowers will have a consistent deposit history and any inconsistent deposits can be used if properly documented.