High-powered executives and other professionals are choosing to rent pets rather than own them. Offering what it calls “a unique alternative to full-time pet ownership,” the California-based FlexPetz, with branches in most major cities, rents out its dogs for $39.95 per day, with a $75 surcharge if the dog is returned late. “It’s like I am the uncle to the dog,” said Manhattan neurologist Farng-Yang Foo. “I can take it out for walks and take care of it. But I don’t have to worry about it being alone during the day.”