The forums from expats are full of information. I can only tell you what I did to get here. First, my home is in Alabama. I drive a total of 30 plus hours (including running all over Laredo, TX) at an average speed of 52 mph due to my heavy load. It was a very hard trip with at least 8 if not 10 fill ups with gasoline both in the US and Mexico.
Next, you must go on line to make an appointment with a Mexican Consulate near you for your FFM, Temp Resident Visa. Take an inventory of your household goods (in English and Spanish) and pay $127 USD to have the Mexican Consulate certify the inventory. You will pay $34 for your FMM which must be renewed within 30 days of your arrival (I was advised to go at the 15 day mark). Your permanent FMM can be for 1 to 4 years. As long as your FMM is not expired you US Tags and TIP (sticker) is good. You do not have to return to the border every 180 days.
With that said, let’s go back to the household goods. The Mexican Consulate Officials will tell you that you need a Pedimento de Importacion. Believe them. I called four or five brokers and they either didn’t provide the service or stated all I need was the Consulate Certificate. I attempted to cross and was turned back. I had a friend in Mexico to call five crossing points from Nogales, Progresso, Pharr, and all the way up and all said the same. I finally found a broker. I had to unload the pick up and trailer, have the items loaded onto a licensed Mexican truck, have it crossed and reloaded the pick up and trailer in Nuevo Laredo (an 8 hour wait, by the way). The cost for this service: $1,500 USD. Do I regret it, wish I had done things different? No, I could not have replaced my stuff here for all of the expenses to include hotels, fuel, and the fee.
The bright red cargo trailer and pick up with a high top camper cover is not a normal site in Mexico and my papers were checked no fewer than 8 times. The trip is not for the faint of heart. It requires patience and humility. At almost 69 I’ve learned those. I had the attitude that I had the rest of my life to get here and kept it the entire way.
The reader can find more details all over the web. These are only my personal experiences and are not meant as a legal guide. When in doubt verify twice!