Any fun rule variations for two person Monopoly?

Basically my friend is constantly getting those themed licensed Monopoly boards from friends and relatives for Christmas and never opens them, but decided he wants to open one up and play. The thing is though I’m the only person willing to play but because it’s just the two of us the game is obviously going to get pretty boring fast. Is there any fun rule variations we can do to make things more interesting? We have various superhero themed ones and thought it would be fun to make an objective mode where you have to secretly assemble a small four person team as one of the win conditions, or do a system where each hero property is “weighted” and we can make superhero fights over property. Anybody got any interesting rules out there?

I used to play with variations like having all fines go to free parking and anyone landing there collected all of it. The trouble is that any rule that puts more money into the game tends to make it interminable. The original rules played rigorously do generally result in a game that terminates in a reasonable time. You have to make hard decisions and sometimes they work out and you win and sometimes badly and you go bankrupt. Just like life.

Short Game variant from the official rules:

When the number of players gets to two our family plays Oligarch’s Rules.

All property cards are shuffled and are dealt to the players.
All money in the bank is shared out. All Houses & hotels are split evenly.
Initially all properties are turned face down.

If you land on a title you hold it’s yours free, a title held by the other can be purchased at face value.
All windfalls paid to you by the bank under the conventional rules are paid to you by your opponent. All fines are paid to them.

Tends to be fast & furious.