BILLY Joel is divesting. The Piano Man, 60, bought two adjacent oceanfront properties for his third wife, Katie Lee Joel, 27, in 2007. Now their marriage is kaput, and he’s trying to sell them for $35 million, reports The Post’s Jennifer Gould Keil. Joel bought the first house for $16.7 million from Roy Scheider. The four-bedroom house — now for sale at $22.5 million — was renovated by celebrity designer Nate Berkus. Later that year, Joel bought a beach bungalow next door on 1.2 acres — now for sale at $12.5 million. Corcoran’s Biana Stepanian has both listings. Joel will stay in his Sag Harbor house, where he’s been romancing Alex Donnelly, an ex-soap star.