What are the visa & residency requirements in Mexico City?

"In order to obtain a visa for travel to Mexico City, one must complete an online application form and provide relevant supporting documents such as a valid passport, proof of financial ability to support travel costs, and a valid return ticket. Other requirements may vary depending on the purpose of the trip. The application must be submitted to a Mexican consulate or embassy in the visitor's home country or to the Immigration Authorities upon arrival in Mexico City. To apply for residency in Mexico City, one must obtain a Mexican national ID, known as the INM form. This is a two step process; first a signed application form needs to be presented to the local immigration office. The application must include proof of identity and proof of the migrant’s nationality. It will then be approved or denied by the immigration officer, who may request additional documents. Once approved, the applicant will receive a stamped version of their INM form and will then be able to apply for a Mexican residency permit," explained one expat living in Mexico City, Mexico.