Rental income is nice but everything is valued in DEC. As I earn everything in-game, I don't really care about the dollar price changes.

Monster Market is a front-end for the shops where you can buy cards. The front-end doing the transaction gets like 5% of the money spent so Monster Market gives you back 3% (60% of their revenue). So in a way, it's like using a credit card and getting some cash back for your purchases. If there is a card you wish to buy and it's already listed on the market, it's best to go there.

!PIZZA