Successful people have learnt that selling something is the key, they learn how to get others interested in what it is that they have to offer and by so doing convert them into potential buyers.
when you market and promote whatever it is that you have to offer, you will get the opportunity to make a sale. Making money draws people around you and they all want to be in your team leading to more opportunities.
No matter what the economy doing, as long as they you can promote and sell, money will come to you. Just remember, once you have made that sale, you have to service you customer with so much value tat they will buy from you again and again. This means you have a whole suite of back-end products that you can sell your customer based on your initial sale. One can make a living selling one thing to each person.
Note that as you are servicing your customer with special care and value, they in turn will encourage and refer you to all their colleagues- so that you can sell many to those people too.