@raveenasen,
Truth be told, any attorneys find it impossible to provide an accurate answer. That is because different attorneys have their own fees to compensate their legal services--with the nature of legal service still in question.
However, the basis of these may be hourly (where the client pays the attorney on an hourly visit that the case or consultation consumes), flat-rate (are legal services that has definite matter of work that needs to be done like divorce or last will fillings), retainers (where the client offers an advance payment and the lawyer puts in an special trust in case of emergencies) or contingent fees (which means that the attorney takes no fee from the client but gets a percentage of the settlement or money after the case).