For WPL3.1.0 (Both PRO and Basic users), you can insert 2 different price ranges in the search widget. One is for listings for sale, the other is for rental listings. For this, please click the "View Fields" button of WPL search widget and then edit the price field and insert 2 price ranges into the text inputs. The top text field is for the price range for listings for sale, the bottom text field is for the price range for rentals. Please check the following figure: