How do MBS make money?

Could you elaborate on the mechanisms through which Mortgage-Backed Securities (MBS) generate revenue? Are they primarily reliant on interest payments from the underlying mortgages, or do they also derive income from other sources? How does the creditworthiness of the borrowers impact the profitability of MBS? Additionally, what role does the secondary market play in determining the value and profitability of these securities? Lastly, are there any inherent risks associated with MBS that investors should be aware of when assessing their potential returns?