Flirtatious husband: Why he wants to marry me?

Kira was an orphan. Her parents died in a car accident when she was nine years old. A lady named Helena Li adopted her. Now that Helena is old and sick, it is Kira's time to repay her the goodness and the love that Helena gave to her. She needs a big amount of money for Helena's chemotherapy. But what if one day, a good looking, rich and influential man will knock on her door and offer to help for Helena's medical expenses in exchange for marriage? Will she accept it? Why would he want to marry her, anyway?