How to you verify a physical address for someone who lives in their RV and uses a mail drop box for their address, which is also the address they use on their driver's license.

Does your CIP require that the physical address is verified? The regs require that the lender have and follow a CIP and form a reasonable belief who the person is.

If your CIP permits, you could use a physical address from the credit bureau report. Is the RV a "nomad" or is it kept in a park? the park address might work. Other options could be the physical address of a relative (with proof).

It will really come down to your bank's CIP.

It does come down to your bank's CIP, however the FFIEC guidance says that a person can use a next of Kin's address or another contact individual. See the footnotes on page 54 of the 2010 FFIEC manual.