Can you guess what is the most common investment of the world's billionaires? It is not high tech, entertainment, or retail. What the world's richest people have in common is that most of them based their fortunes on owning land and buildings -- the fast moving world of commercial real estate.

What most people don't realize is that it is relatively easily to get into the business of commercial real estate. All you need to find is a few good agents and access to some capital to get started. Once you start renting out properties, you can repay the initial investors and then just rely on your own profits.

How does it work? Simple. First, drive downtown and find some property that looks a bit dilapidated. No matter what condition it is, if the location is good you can make very nice money. There are always building that do not see their potential because the builders are not giving the building or the tenants the attention they both need. Buildings that have a lot of vacancy can often be bought for far less than their market value.

As soon as you have the title get a team of contractors in to clean up the place. Stick in a gym and a coffee shop and start marketing. Don't expect businesses to find you, go to them. Look for stable clients like well established law firms and offer to pay all their moving expenses and give all the partners free gym membership. You will make back all the money you spend very quickly in rent.

Just remember, all you have to do is listen to your clients. Keep them happy and they will keep you happy. Sometime all it takes is a monthly free lunch to get people to feel great that they are your tenants. Of course, don't sit still. As soon as you have enough capital for another building go for it. The more commercial real estate you own, the more you can control the market.