I've sawed my share of Black Locust that grows around southwestern PA and it's a tough tree to get decent boards from or make money on.
As Gene mentioned, the heartwood is what you're after, and it does make good decking for exposed applications (trailers, truck beds, industrial decks). However, for residential applications I might hesitate since it tends to splinter easily. So a dock or an outdoor deck or any other place where barefoot traffic would be present wouldn't be a good application. Also, a lot of south american species have good water and rot resistance, are more plentiful and more attractive than Black Locust, and are therefore preferred by builders and contractors.
Locust isn't the best long-lived species, and tends to form bark pockets and open voids within the trunk. Many logs I've received have insects, or water cracks, or excessive branching or all three. I usually get them from tree services, so they are yard trees, since most loggers I know around here won't even pull locust up to the landings.
It is difficult to saw, so if you plan to do so, anticipate the extra costs. I have to change blades, sometimes as often as hourly when I saw it.
I took a quick look around your DNR / forest service and it looks like white oak grows well in many parts of Minnesota. If I were considering your plan, I might also look at White Oak as well. It is similar to Black Locust in that it has good water and rot resistance, is durable and strong, and has the added benefit of being more attractive when sawn. Black Locust is an orangy color when first sawn, but quickly ozidizes to a muted brown that shows defects readily.
White Oak is not nearly as harsh on the tools and sawblades. I rarely have any trouble selling White Oak. In fact, more often I have trouble getting ahold of the logs to saw.
As with Black Locust, White Oak needs competition to prevent sprawling branches, so if you plant it, do so densely, so that the trees grow up, rather than out.
Check out these links:
http://www.bachmans.com/Garden-Care/divHomePage.html?cnb=GardenCare&categoryCo
de=02&pageIndex=_pageIndexToken_oaks
http://www.minnesotaforests.com/resou
rces/pdfs/funactivities/treesofminnesota.pdf
Also search around for "white oak cultivation in Minnesota" for some more good resources.
It looks like White Oak is plentiful in parts of Minnesota already, so inexpensive sources of adapted seeds should be readily available.
Best of luck.