National Lampoon's Gold Diggers (movie, 2003)

Calvin and Leonard, two broke losers, are arrested for trying to rob rich old sisters Doris and Betty. The women have a change of heart, drop the charges and invite the the boys over to their mansion. Calvin decides he and Leonard should marry the women, and, when they soon die, live off the inheritance. The ladies, however, have run into their own financial troubles and wed the boys with plans of murdering them for insurance money.