I will leave it to you to decide the expected/unexpected debate but in terms of planning, the answer is a resounding yes. Even if you want to do everything yourself, it is always good to have a backup. Many small business owners have colleagues that share the same work. You could develop a reciprocal arrangement whereby holidays (which are critical to the success of your business by the way), and illness.can be covered over the short term.
Yes, businesses that offer the same services can be your competition but remember that even the big companies do quiet deals that never make the news. Business shouldn't be cutthroat, but rather more collegial and civilized.
I think as a smaller-sized company, at the end of the day I want it be known that I played fair, not that I had the most toys. It is all about integrity. You don't have to advertise it but it will become known in the industry. Bad news travels faster than good news, but the good news will get out there.
So think about how you take care of your business.