A 2 player scenario: I have two rent cards, worth 2M each. I can see that my opponent has 6M in their bank - consisting of a 4M card and two x 1M cards. If I play my first rent card they are likely to give me the two x 1M cards. If I then play my second rent card (within the same turn) they will be forced to give me their 4M card as well (as they can’t get change)... Is that just good strategy? Or is my opponent entitled to wait until I’ve played all my cards in that turn so that they will know the total amount they will need to pay me? (Thus avoiding having to give me the 4M and the two x 1M cards.)
Each card play is separate, so your strategy works just fine.
From Play Rules
Each player can play up to 3 cards per turn. A play is considered any time a card is played on the table
And from Rent Rules
Once played, this wild rent card forces only one other player (whom you choose) to pay rent for the properties you choose based on what is laid in front of you.