In the NES Monopoly, you can play with up to eight players, either human or computer.

And before the dice roll, you can press Select to bring up a screen

where you can choose a player to change from human to computer, and vice versa

I presume that this is because games of Monopoly can take just shy of forever to play, and if people join or leave the game, you can keep it going.

But if you're playing against computer opponents, you can also use this feature to turn a CPU player into a human one, then have it give you all of its money, then turn control back over so that you win the game.

So, yeah, it's a little underhanded, but if you're not playing against actual people, no problem.