By Abigail O’Leary A couple trying to evict a squatter from their $2million dream home claim he caused a sewage flood at the property. Susana and Joseph Landa, both 68, bought a mansion in Douglaston, Queens, for $2million (£1.58 million) in October. They planned to use the home for their sons to help care for their son Alex, who has Down’s Syndrome, in their new home. But now, they’re having to take a man named Brett Flores to court to get him out of the property. Joseph explained: “It has become a nightmare, a total nightmare. Even though they bought their home over four months ago, they sti…