De-humidifiers are costly devices to run 24/hrs/day and run into the same problem as heating; if you live in an old drafty house, getting the moisture down is the same problem as trying to keep the heat in during winter months as like heat easily escapes, moisture forming overnight easily enters in the house. (dew point).
Before renting or buying a house, look for tell tale signs of moisture or humidity problems on the walls and around the windows. Most people don't bother with de-humidifiers and get by with no health issues so it depends on occupancy needs.