1% of Anything (2003)

In both dramas the leading male's inheritance is threatened by the leading female and they eventually fall in love.

There are many similarities between the shows, ie:
-Grumpy male lead with a heart of gold hidden under protective layers of absolute douchiness
- Rich to poor female lead with a smile that's brighter than the sun
- The better guy overall second lead (at least before the male lead softens)
- and many more pre-2015 kdrama tropes.

Male characters have similar personalities (Jealous and aggressive but committed)
it does have the rich man/ poor woman theme but 1% of anything have a much older couple and a bit dated

They are both about a grandfather trying to force his grandson into an arranged marriage,
In BP the Ml and FL enter into a contract relationship to fool the grandfather so he will stop making the male lead go on dates.
In 1% it is the grandfather that specifies that the male lead and female lead get together because the female lead was nice to the grandfather .

the second leads remind me of each other
the guys both misunderstand the girl to be someone else and start pursuing them without getting the full details

Similar plot. Kind-hearted woman saves elderly man, who then decides she deserves his entire fortune. Arrogant grandson wants fortune and after hijenks falls in love with woman.

In both drama's the main characters, in the beginning, don't get along, but due to a contract they continue to be in each others life, and in the end start liking each other.

Something about 1 Percent is a remake of 1% of anything. I think the earlier version is quite charming.

They both contain that fluffy and cute romance between the characters. I thought both match each other well.

both dramas both have issues with a huge inheritance being given to a female although it was the male's family own first.