Where is the best place to get a non-resident fishing license? How much do they cost? How long does it take to get one? Is it something that has to be done in advance or can I wait till the day before the trip?

You can get them online (google Minnesota DNR-you can get the price there too) or from most outfitters, bait shops, lots of gas stations, etc. (no problem). It only takes a couple of minutes.

fishfinder2

Non resident licenses are available at any outlet, and all licenses in Minnesota are issued electronically. You will need a drivers, and have to provide a social security number, the 1st time you purchase. After that, you will have a DNR number on your license which is forever (you just need to be able to produce it)All your info is then in the system. Your drivers license number will also get you a license any year after your initial purchase. Costs are as follows:
Non resident 3 day-$21, 7 day-$25, NR seasonal $35, good from March 1st to February 28th of the next year. Trout stamp $10. You will have to pay, I believe, a $3.50 additional issuing charge when purchasing online.