collateral analysis: servicer, seller, issuer

when analyzing quality of collateral, we need to analyze cashflows. for the following parties, whose party 's cashflow should be analyzed? issuer servicer seller collateral I just need a confirmation. I would analyze cashflow from collateral, seller. issuer and servicer are usually the same, and their cashflow is not relavent?? this is a grey area for me.

someone help me?..