Parking at the Minneapolis St Paul Airport is iffy and expensive- a minimum of $12 per day at the Humphrey Terminal, and $16 per day at the Lindbergh.
Park 'N Fly is located just south of the Humphrey Terminal, and offers parking for $8 per day with online booking and reservations. They provide a shuttle bus to and from both terminals. A much better deal. I calculated that a cab to and from the airport would cost me about $25 each way including tips, and this parking on a 5 day trip cost less than that and was a lot less hassle.