The biggest 'ah-ha' moment in real-estate investing for me was when I realised that banks were happy to lend you a lot more money than you were capable of paying off.<p>In other words, the limiting factor was not the amount of money you could borrow, it was the amount of debt you were capable of servicing.<p>Many times you read in the newspaper of the young couple who have built up a real-estate portfolio worth millions in just a year or two. And everybody is envious. Except when a little while later, some minor upset causes that whole house of cards to collapse, because their suddenly reduced cash-flow just couldn't cope with the cost of servicing all their debt commitments.