Re the guys living in Florida and their Montana LLC:
Florida doesn't have a personal property tax, so the only thing the LLC affects is sales tax at the time of purchase. With the vehicles owned and titled in Montana, you pay Montana sales tax ($0) instead of Florida sales tax (6%). But if they stay (reside) in Florida very long and keep those vehicles in the state, Florida does require that the vehicles obtain a Florida title & tags. There is a title transfer fee and a one-time "new-to-Florida" vehicle impact fee ($225). However, that is still much less than Fl sales tax would have been.
That would be a legitimate "tax avoidance" as long as the vehicle actually was out-of-state and later moved into Florida. Where it gets questionable is if the vehicle is bought in Florida, titled & taxed in Montana, but the vehicle itself never left Florida. Or was out of Florida for only a few days or weeks. If detected, the state would likely claim that the LLC was exclusively used to avoid paying Florida taxes on a Florida vehicle and that would constitute tax evasion under Florida law. I've never heard of that being applied to snowbirds (part time residents), but I have heard of prosecutions for of those who reside long term in Florida but tried to title their vehicles in some low or no tax state.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL