There are mail forwarding business that provide people who are transient (often RV dwellers who are on the road rather than living in one RV community) with a street address. The mail forwarding business will either scan the incoming mail envelopes and post them in a secure online private box for you to look at over the Internet or they will bundle the mail and physically ship it to you. Even though you get a street address through a mail service, you do not automatically get to claim that location as your legal residence. State laws about residency typically require you to be physically located in the state for a particular number of days each year. The list of mail forwarding services at the bottom of this page identifies two that will help you to register your vehicle and establish residence in their states.
Here is how the mail scanning services generally work: The company scans the envelopes that come for you. You go online and view the envelopes in your password protected online box and identify any that the service should open and scan. The service will then scan those documents straight into your confidential online box.
These services charge minimal flat rate fees, typically by the month or the quarter, to receive your mail. Depending on the company and the range of services you select, they may charge an additional per-page scanning fee for any documents that they take out of your envelopes. In other words, your flat rate can include just the envelope scanning or it can also include the document scanning as well. Of course, you do not have to register for the scanning service. If the mail service is in your city you can go there to get your physical mail every couple of weeks or once a month or on whatever schedule you establish with the mail forwarding service.
Examples of companies that provide mail forwarding and mail scanning services:
http://www.yourbestaddress.com/ (also provides vehicle registration services)
http://www.texashomebase.com/texasdomicileinfo.html (includes information about vehicle registration and establishing legal residency in Texas even if you are only there for part of each year)
See the cities in which Earth Class provides street addresses https://www.earthclassmail.com/addresses