You'd need to play a Speed Die game to get this, As the third dice has a maximum number of three, you'd need to throw a 6+6+3 to hit 15.
You could do an offline game with four controllers, bankrupt 3P and 4P, buy properties for 1P on auctions on the cheap, and then mortgage every property so that both you and 2P won't need to pay rent. From here, just keep throwing the dice until you hit 15.
Totally by luck, I guess. It took me over 45 minutes to finally get it.
Update: El Geeko Grande posted that you could start a custom game with all of the properties dealt and only play with 2 humans to try for this one (see comments).