The 72 rule is the number that you divide by to determine how long you get your investment back (or how long it takes a property to double!! in value) i.e. with property going up in value at 10 % per annum then the property will take 7.2 years to double. ( It then doubles again of course ) At 5% it will take 14.4 years to double. Property has pretty much been on a consistent close to or around 10% since these records have been kept. At 15% which has been happening lately it will take 5 years to double. So no matter which way you look at it properties double every 5-15 years! A single $210,000 property could double in 7 years, that is $30,000 per annum!!, where a $420,000 property could double in 7 years, that is $60,000 per annum!!,