Tax differences between permanent and temporary? (Guadalajara)

Anyone know what the tax liabilities are for foreigners living in Mexico? Is there a difference in the taxes you pay between a temporary residency (residencia temporal) vs. a permanent visa (residente permanente)? For example my parents want to retire in Mexico and qualify for both types of visas. They have retirement income and cars and are worried about having to pay Mexican income tax and annual Mexican car tax. We can't seem to get a clear answer concerning the taxation differences between the types of residencies and would be grateful to anyone who can give some information.