I tend to watch lighter dramas than the ones you've already got on your list, so I've got a few romcom dating or marriage contracts and zero kept women.
Love in Contract - she rents herself out as a beard/fake fiance. It starts out purely transactional.
Marriage Not Dating - Enemies to lovers, contractual arrangement so his mom won't take away his apartment
Because this Is My First Life - contractual marriage to assist a house-poor man
She and Her Perfect Husband - mutual convenience marriage
Marriage Contract - organ donation contract
Hello Mr. Gu - contract marriage, opposites attract
Coffee Prince - contract dating to stop parental interference about getting the ML married off.
Cinderella and the Four Knights - she's hired by a rich old guy to live in his house and adult his sons
