Actually, not all the people in the inner city are wealthy.
With such poor productivity, it's impossible to support that many rentier classes.
Most of the people in the inner city still have to rely on their own work to support themselves and their families. They just have a relatively more substantial family background, better education, and more plentiful opportunities.
They work as industrial workers, staff in factories and enterprises, clerical workers in trade associations, and officials under the Alliance Government... They have a stable and even somewhat respectable job, but that's all they have for their livelihood.
In fact, under the new system designed by Gu Hang, if these people did their jobs well, their opportunities would still be much greater than those of the people outside the city. A more comprehensive education and a wealth of work experience were their advantages.