The biggest investment most people make is a house. Then there's the cost of maintenance, repairs and improvements. After a few years remodeling is a possibility, but insurance is a must. With a house it's always something; but as long as the interest on mortgages is tax deductible, homeowners can sleep in a tax shelter.

Those who are skittish about investing in the stock market can let their money ride - on tractors. Antique tractor collecting became popular in the 1970's. Some names are familiar - John Deere and Case - and some aren't - Oliver and Silver King. Some are already restored and others are waiting for hope to be restored. As the number of tractor aficionados has grown, prices have increased. Prices drastically increased in recent years because of European investors benefiting from the exchange rate. Prices of older tractors can double in a year - making tractors a down-to-earth investment.

Then there's Elon Musk's out-of-this-world investment. Musk is the 37-year-old, mega-millionaire co-founder of PayPal, who invested $100 million of his own money in Space X, a low-budget rocket company. His goal is to radically reduce the cost of putting objects into space. Unfortunately, Musk's three attempts to put a Falcon rocket into orbit have failed - so it seems some things do require a rocket scientist.

No rocket scientist is needed to get to Mars - Mars, the chocolate manufacturer, that is. That Mars is investing $10 million to study the genetic makeup of cocoa. The world's cocoa supply is produced by 6 1/2 million subsistence farmers in Africa and the Americas; but their plants are suffering from disease, pests and climate change. Knowing cocoa's genetic makeup will enable more resistant plants to be grown and Mars is willing to provide its information to anyone - even to the Hershey Chocolate Company. That is an offer that should be sealed with a kiss.

Finally, the owners of an upscale supermarket in Chevy Chase, Maryland have sealed the deal on investing $7,000 a year in a car wash for their shopping carts. According to the supermarket owners, shopping carts are more germ-infested than pay phones, soap dispensers and toilet seats in public restrooms. By spraying a peroxide-based mist on the carts, the system supposedly eliminates 99.9% of the germs. The company that makes the cart wash system has sold 20 units in the U.S. and South Korea. Unfortunately, that is far from a clean sweep.