Noting that I just bought a vehicle that's in Florida (and was in Nevada before that), IMO any transportation costs are worth it because once rust starts it's a huge chore to arrest/correct it. So I myself try to find vehicles from rust-free areas.
The shipping costs can vary dramatically depending on who you use, from a few hundred to a few thousand, but IMO it's money well-spent. You should be able to get something from the South shipped up to MI for $1500 or less, and I'd just budget that into the cost. See what a google of Central Dispatch brings up, they often have cheap rates if you're flexible about the date.
But OTOH, you can sometimes luck out and find a vehicle from a rusty-car state that's still just fine. Just depends on the individual car...but don't be surprised if you have to pay a hefty premium for that rust-free condition anyhow.
The way I see it, buying a vehicle is all about condition, and you gotta pay for something nice. Trying to save money in the wrong way is simply a bad idea. Sorta like buying vehicles sight-unseen; sometimes you can get lucky and everything turns out fine, but other times the money you save is a very expensive mistake.