in the book maus were the Jews allowed to have a normal job other than them having to sell stuff to provide for their families?

No, once the Jews were in the camps they did not have normal jobs. As the Nazis

moved into the cities, Jewish businesses were destroyed and taken. Their valuables were taken. Ghettos became home for the Jews before their removal, but they no longer held real jobs......... if their talents were of use to the Nazis they were used. "Used" being the operative word.