He lives in a society that has by the time of the novel become bascially socialist, which is tyrannical to him. The long-term goal of the doctor and the rest of the capitalists is to cause global society to completely collapse, so that it can be rebuilt along Objectivist lines (including an amendment to the Consitution forbidding Congress from enacting laws abriding the conduct of commerce).
At the present, he makes money treating the rest of capitalists' medical needs.