Horizon: An American Saga – Chapter 1,” the Western movie Kevin Costner directed, co-wrote and stars in, tanked at the box office last weekend, grossing a paltry $11 million.More alarming is that the three-hour film, which the former “Yellowstone” star reportedly put $38 million of his own money into, is the first of a four-part series. The second entry hits theaters quickly in August, and the third is currently filming. According to Vanity Fair, Costner, 69, plans to devote $100 million of his own cash to the ambitious effort.“I’ve mortgaged 10 acres on the water in Santa Barbara where I was going to build my last house,” Costner told Deadline.