You can get just about anything online these days and that includes real estate.  There is a site I frequent called BillyLand that offers rural listings with a contract for deed.  You either place a bid or pay the seller's asking price outright and that serves as a down payment on the land.  The remaining installments are made in monthly payments to BillyLand.

I have never purchased anything from them, but they have excellent reviews and a great rating with the BBB.  There are currently no listings for Montana, but I have seen them before, so I'm keeping an eye out.

Real Estate is typically a great investment, but be warned, some of these properties are way off grid and might not be as good of a deal as you think.  If everything checks out, it might be a great way to get your 100 acre post retirement hideaway lined up.