No single client should make up more than 10% of your overall revenue. Since that company would have a lot of control over the amount of money you make per year, this could be detrimental to your long-term success.
I realize that it may sound crazy if you're just starting out, but sometimes you simply have to fire clients. They'll drive you insane if you let them, and working for them simply isn't worth the money. Clients in this category include those who pay late or don't meet their contract commitments. Many management consultants say that you should fire the bottom 20% of your client list every year.
Clients with unrealistic demands simply have to go before your sanity goes. Learn more about balancing your portfolio and dealing with difficult clients in the full article (link above).
Posted by Joshua Feinberg