A father and son who own hundreds of rental properties across Dallas have been accused in a lawsuit of keeping tenants in “unspeakably squalid conditions” while requiring them to pay for pest control. In a complaint filed last week, tenants Joanna Pena and Sergio Rendon also claim that Hanna Khraish, his son Khraish H. Khraish and their company, HMK Ltd., are breaking state law by using a …