What would you do, would you buy a property that you have to add $50 a week towards in today’s market considering the 72 rule . The 72 rule is the number you divide with the inflation rate to see how long it will take for the property to double in value. How many of those can you do at once if you have to top up $50 each per week. For the serious investor Income property is a must but for the first time investor buying one or two homes that require a top up maybe required.