If you're unfamiliar with the concept of arbitrage, here's how it works. Wikipedia describes an arbitrage as effectively, "the practice of taking advantage of a price difference between two or more markets: striking a combination of matching deals that capitalize upon the imbalance, the profit being the difference between the market prices." Clothier was able to identify arbitrage opportunities in the grocery industry with precision. 
Invest in real estate. Relatively stable assets like rental properties, or potential development land in a steadily growing area is a good way to build wealth. As with any investment, there are no guarantees. Many people, however, have done quite well with real estate. Such investments are likely to appreciate in value over time. For example, some people think that an apartment in Manhattan is almost guaranteed to increase in value over any five-year period.
Try flipping houses if you have experience with making home repairs. As you may know from watching popular home improvement shows, flipping homes involves buying up a lower valued property that needs work, and then fixing it up for resell. To get started, you’ll need to have financing either through a bank a partner. Then, you can buy a property that’s priced below market value. After you renovate the property, you may be able to sell it for a profit.[10]
Become a dog walker if you live in an area where they are in demand. You can walk dogs for people who own dogs but who are too busy to walk them. However, this can be a demanding job, especially if you end up walking a few dogs at once or if you are walking dogs throughout the day, so ensure that you have the physical stamina for this type of job.[13]