Regarding the subject matter of business, I have always stressed to my colleagues that everything boils down to buying and selling. In every human contact, you are either selling or being sold on a product, service or idea. Think about it.
At the grocery store, you are buying much needed groceries while the store profits from getting them to you. At your job, you are selling your time and service, and your employer is buying that time/service from you. Even your son or daughter is selling you the idea of why they need that new toy and you are happily buying it. My son would even go the extra length of explaining how convenient it would be for the entire family if he does not have to wrestle with his sibling over the old toy.
While both parties (buyer and seller) in the transaction end up with what they expected from the deal, the seller generally wins in terms of financial profits. The seller has the greater advantage of leverage. Apart from the rewards of profits, the seller can sell to MORE buyers at the SAME time while doing the SAME amount of work. The better the leverage, the higher the profits.
At your job, there is only one YOU rendering the service and you are paid a fixed rate for each hour you render that service. How about if you are able to clone yourself and two or more of you are able to work at the same time, rendering more of those services?
This is exactly why a corporation like McDonald's can be so profitable: they have "cloned" their locations and representatives many times over and they have succeeded in selling to the entire planet. True sellers can make profits even while they sleep. The hard work goes into building the system for accomplishing this. It is like preparing the soil and then planting seeds in a farm. The growth and harvest of the plants come automatically.
The Internet has changed the commerce game for everyone. I encourage you to visit AliBaba.com for ideas on what you can sell. Thousands of manufacturers have listed millions of their products on the website. You can order these products for a great bargain and sell to others at a substantial profit. Browse through the product categories and find something that catches your attention.
You can even take it to a higher level: help others buy and sell. Create a system where anyone with a need can contact you and anyone with a product can give you a catalog of what they have to offer. Connect both parties and keep a portion of the seller's profits as commission. With this knowledge, you can sell EVERYTHING on the planet!
The bottom line is this: find something to sell and sell it to as many people as you can in the most effective manner possible. You can never go wrong as a sales person. Sellers are usually winners.