Luxury hotels are out, but lower-priced hostels are in in South Florida. Developer Nathan Lieberman learned the hard way that the market wouldn’t support his 12-story Hollywood Beach condo hotel with stores, pools and other amenities. But he pressed on and shifted his business model, and his hotel-hostel, with both private and shared rooms for older and younger travelers who enjoy meeting fellow guests, has made an Ikea-furnished splash. The new wave of European-style lodgings is spearheaded by veteran hoteliers who know how to maximize business — using multiple websites to help fill rooms and offering group rates for watersports and tours to boost revenues, for example. While there are a mere handful of hostel-hotels in South Florida now, they are a successful formula in a difficult market.