2. Not all households are alike. Say you have three rental houses. House 1 has two young professional couples in it who are each looking to buy a place on their own. House 2 has four low income workers living in cramped conditions. House 3 also has four low income workers living in cramped conditions. The landlords of Houses 2 and 3 want to sell up for whatever reason (e.g., high current prices, concern about rent control/regulation, hitting retirement age). 8 low-income people are thus evicted and have to find accommodation somewhere other than Houses 1, 2, or 3 (none are available during the sales process). Our young professional couples buy Houses 2 and 3 and get on with their lives in more comfortable homes. House 1 only comes onto the rental market after the sales process and is of no use to the 8. So, when the dust settles, we're down 1 rental unit net solely because of changes in how the three houses are occupied.