“How many buildings will have to burn?”It’s not a rhetorical question that Ben Cantu is asking.He sees the obvious connection between “fires of suspicious origin” and the fact buildings that have a tendency to go up in flames in Manteca have been gathering places for the homeless.Are there arsonists among the homeless? If that were the case Manteca would have looked like parts of Napa and Santa Rosa years ago.They are homeless warming fires in most cases or — as has happened in the past — cooking fires that have gotten out of control. In a way it’s like an improperly attended or inadequately extinguished camp fire that gets out of control and sparks a forest fire.Cantu is making his third run for mayor of Manteca in November.