Apartment buildings often use 100 Gallon Commercial Grade water heater to provide hot water to the entire building. It is cheaper than servicing individual water heaters. You will need about one 100 Gallon Commercial Grade water heater for every 16 units. They last about 10 years if no maintenance is done on them… If you attach a hose and clean out the entire water heater once a year, they last another 3-5 years. The rusty sediment on the bottom of the tank compounds the rusting. So… Do a little preventative maintenance and you save a few bucks!
Water heaters range in price. But, currently water heaters are about $4,000 to $4,500 installed.