Although in the last few generations the idea or marring for money is not popular, it was considered normal in the past. Throughout history, marriages were made for strategic alliances, economic gain and other unromantic reasons. Women need support while they are pregnant and that's why they look for a partner, who will financially take care of them.
We don't have to like it, but it is natural. In the same way, older men are looking for a younger, healthy woman who can get pregnant easily and is suitable to raise their children. If everything goes as they wish, there is no problem – the woman is getting her financial security in exchange for taking care of children.
The problem is when man gets broke or the woman loses her ability to give birth and raise children. That pair is for fair weather only: when times are bad, they split. Marriage is a great commitment and promise to stay together even if times are bad. Think twice before you chose this way to become rich.