Carlos, the main documents/information needed for a buyer are:
Two years residence and employment history.
Current paystubs, current W2s
Two years tax returns if self employed or show other types of income (rental income, interest/dividends, etc.). Personal and corporate if applicable.
Two months asset statements for all accounts where funds for closing and reserves are coming from
Credit will also be run
Some lenders, (like the one that helps many of my buyer clients), have alternative documentation programs where tax returns may not be required, e.g., bank statement programs for self employed if income from returns don’t substantiate qualifying income.