"To the OP, the law-firm in Missoula you were referred to is to setup a Montana based LLC that "owns" your RV. Be-advised that some states (including Washington, California and Colorado) consider this tax-fraud."
I rather doubt that a resident of "Mo" as noted in the OP really cares what the authorities in WA, CA, or CO thinks of a MT LLC that is owned by a resident of that state! By the way, the LLC does, in FACT, OWN the RV. The LLC is the registered legal owner of the vehicle!
On a side note, if the RV is 11 years old or older, it can be registered in Montana with PERMANENT registration! No renewal is EVER required, until the title is transferred! NO inspections are required, either! If it is a trailer, it will be permanently registered even if brand new!
Yes, joint ownership IS possible. My Jeep has been in joint ownership since the day we bought it; it is in my name and my son's name. The Jeep is registered and titled in Montana, where I live. My son lives in California. If the OP has a relative or good friend who lives in a state where it would be advantageous to title and register his RV, it might bear looking in to.
