Work crews have demolished a run-down Las Vegas condo complex as a builder pushes ahead with plans for a new housing tract. The sprawling former Paradise Spa complex, which had a history of fires and squatters , has been reduced to piles of rubble. Located several miles south of the Strip, the site is expected to be cleared by September, and builder Taylor Morrison Home Corp. plans to start construction of model homes next February, according to Kent Lay, Las Vegas division president for the company. Last year, Clark County commissioners approved plans by Arizona-based Taylor Morrison to build 275 homes on the 28-acre site at the southeast corner of Las Vegas Boulevard and Serene Avenue. The new community will be called Paradise Encore, and home sales are expected to start in the first or second quarter of next year, the builder said this week.…