Far worse even than that althor, is their destruction of communities. a given locality is zoned for particular purposes and engineered for a particular number of people. Imagine that a neighborhood has 500 houses. This means roughly 1500 to 2000 people live there - they place known pressures on the infrastructure, the trash collection, roads, parking, water supply and sewer, fire, police, traffic., schools, shopping, entertainment, communications, gas, electricity and the like. Now imagine that every other home has a garage illegaly converted to a second family dwelling. I could estimate that same 500 houses might contain as many as 6000. Planners never had that in mind and all of the services and infrastructure gets a tremendous hit - communities can and do falter under the load and little can be done to anticipate this uncontroled and even unmeasured growth. I saw horrible things, three or four families living in one house, each family making leanto additions to single rooms where they all lived, illegal livestock being raised in small backyards, 6 or 7 cars parked in the street and front yards of houses. I recall one home that had 11 separate TV dishes . These were single family dwellings, two or perhaps three bedrooms and two baths supporting as many as 12 or 13 occupants each. Imagine what this does to the municipality. Mind you these were in moderate income, ordinarily quiet and reserved neighborhoods, not tenement districts or apartments. The overflowing homes were taxed as single family homes. Entire communites can succumb to this sort of rot in short order - and the rats, the mosqitos that grew in collected water in discarded containers where that no inspectors could possibly contend. Illegal imigration is hard on any society.