Before boarding: online, at a US consulate, at a border module, or at the Banjercito module inside the Pichilingue ferry terminal (La Paz). No module is listed at Santa Rosalía.
Documents
Passport or US Passport Card (foreigners); green card, non-Mexican passport, Passport Card or work visa valid 1+ year (Mexicans living abroad)
Immigration form issued by INM (foreigners); INM pre-authorization if applying online or at a consulate
Proof of ownership: title or current registration
If financed: credit contract in your name dated within 3 months
If leased: lease contract showing the VIN plus a letter from the leasing company authorizing the import
Credit or debit card in the importer's name (cash only at border modules)
Motorhome (casa rodante) permit, at a border module or US consulateOfficial source
$51 USD + IVA tax
IVA is added. Mexpro (an insurer) says Mexican RV insurance is required to obtain an RV permit; the Banjercito requirements list fetched does not mention insurance.
Guarantee deposit for a motorhome (casa rodante) permitOfficial source
Official pages say every importer pays a guarantee deposit and give one table by model year, but none of the pages fetched states an amount specific to motorhomes. Mexpro's RV page does not mention a deposit.