It is very hard to get around residency because someone living at that address needs to pay income tax. You can even rebate back the occupancy tax via the income tax or sales tax systems.<p>If you don’t want to do this you can do random surveys of the suspect property (say any property without a taxpayer) and if it is unoccupied more than a few times and not registered as unoccupied then a big fine results.<p>Finally, the owner does not need to sell, just have tenants. What you want to avoid is housing sitting empty or only being used as a holiday home a couple of weeks a year.