The Donald has recently suggested that He would like to look into buying Greenland from Denmark in the same manner that Alaska was purchased from the Russians. I think the Danes would be smart to look into selling it as it is costing them money every year with very little returns for their investments so far.
The alternative might well be that Donald declares Greenland a national security threat and invades them so that the world remains safe for democracy
I would suggest to the Danes that as any other real estate transaction that they put it on the open market and see how much Russia or China are willing to offer