Fortunately (or unfortunately depending on your perspective) Mexico is very relaxed at tax enforcement. If you’re already being taxed on your income from the US, you likely won’t have to worry about Mexican taxes unless you’re involved in some commercial activity in Mexico or have Mexican-sourced income.
I’ve lived in Mexico for several years while working online for a company in Canada. Since I am already taxed by Canada, an accountant here in Mexico said that I don’t have to worry about taxes. He explained that because of the double-tax treaty, it’s not worth it for the Mexican government to go after Canadian and American expats. Canada has a higher tax rate so there wouldn’t be any tax owing in Mexico after submitting a Mexican return, thus unnecessary paperwork for everyone. I consider this an advantage of living in Mexico versus similar countries like Colombia (where the government is a lot stricter on foreigners submitting tax returns).
However, I consider this a double-edged sword as Mexico is in very bad shape because of the lack of public funds. Sure you will save on taxes and from a lower cost of living by living here, but you will pay indirectly through other means such as your health and security. For tourists and short-term nomads, it’s a great place and there are lots of positives you probably already know about. However, for longer-term stays, I think the country is too hazardous to live in if health and security are important to you.
Imagine having to use bottled water to wash your teeth every day because the tap water could be poisonous.
Imagine having a police force that is so corrupt that they go around in groups looking to rob tourists at night in popular beach towns and entire police departments are regularly replaced by the army due to links to criminal gangs.
Imagine so many people disappearing all the time that family members have to pay private investigators to look for their loved ones since the police is either overwhelmed or doesn’t care.
Imagine companies like Coca-Cola and Pepsico having so much control that health experts cannot combat the diabetes epidemic since they fear for their lives and are targeted with government surveillance.
Imagine the air being so polluted in major cities that it causes 1 out of 17 deaths and takes years out of your life expectancy.
Imagine having to find out through the FDA (a foreign health watchdog) that 84% of hand sanitizers in Mexico have Methanol, a poisonous substance that damages your organs.
Imagine having to find out through the FDA (a foreign health watchdog) that a popular bottled water brand in your country has high amounts of arsenic.
I could go on forever with this list, but I think you get the idea. Just keep these things in mind and remember that ‘you get what you pay for’.