Ok so, in mega cities, the informal economy is quite large due to the lack of formal job oppotunities. This involves selling hand made goods, picking through trash and selling off recyclables and offering services such as sewing. This is a problem because it means that these people don't pay tax, meaning less money for the govenment and thus they can't improve the infrastructure, trapping the city in a cycle of poverty. It also increases the likley hood of exploitation as there are no regulations, and sale prices can be hyper inflated based on supply and demand.
So informal economies are the main way people respond to employment issues, however this is clearly an issue in itsself so some better solutions include the self help project of the Grameen bank in Dhaka which gives out small long term loans to people to help them get into the workforce.
There are also heaps of other self help projects, NGO responses and government intervention solutions in other mega cities which are worth looking into cause it's pretty interesting, but yeah, the ones I mainly focused on during HSC prep were the Grameen bank self help project and the flawed response that is the informal economy. So hopefully that answers your question