the plot isnt usually similar but the cliches are almost always there (Amnesia,birth secret,relative that gets bought off and screws the Main or Female lead)
One person is rich the other is poor,the family is againist the relationship
90% of the time there is an evil person that "gets taken care of" 10 episodes prior to the ending.
EVIL 2NDFL/stepmom is a must as well.
Edit:I would suggest weekend drama over daily drama for sure if you want something lengthy.