Is it permissible to sell a visa obtained from the state for a symbolic fee, whether with or without the sponsor's knowledge, and is the money earned from its sale unlawful? What is the solution in this situation?

It is not permissible to sell a visa, as it involves fraud and the unlawful acquisition of wealth, whether the sponsor is aware of it or not. The sin is greater if it is done without his knowledge, due to the breach of trust involved.