For sustaining of a WSS over its design period, operation and maintenance cost should be fully recovered from the users. Therefore, willingness to pay and affordability survey of households in small and medium towns is a prerequisite for selection of proper scheme, its implementation and financial sustainability. This paper suggests basic criteria for designing the survey format to derive appropriate information, methodology to assess willingness to pay and level of affordability of beneficiaries and its usefulness to decide the requirements of the scheme. The methodology is used to assess willingness to pay and affordability of consumers in three towns and the results are presented. Such an approach is found to be useful in planning of new WSS with its financial sustainability.