Okay, this is not a mistake I made, but something I learned along the way planting the church
Be absolutely sure of your call.
It is a guarantee that you will face some very tough times while planting a church. These are no less tough than problems faced when pastoring an established church, but different. It is absolutely vital that you hold fast to your call to church planting, and that you know there is nothing else God would rather have you do.
While in college one of my ministry professors said, "If you can do anything at all besides pastor and have a clear conscience...do it!" I agree. There is no need to suffer the trials of planting a church unless that is God's call for you.
Some would say that the Call of God on a person's life is only a personal thing. I think that is absolutely wrong and rejects biblical teaching concerning God's use of community. Our call to ministry is both personal and corporate. God speaks to and confirms His call in my life to me through my times of prayer, preparation, gifting, and His voice. But, God also use our community to call us into ministry. It is often other people who see it most clearly in our lives. They recognize the gifting and call sometimes sooner than we do, but they also recognize the lack of call despite our earnest attempts to believe we have a personal call.
This tough for many. Because the call is most often recognized in a personal setting, we often forget about the corporate aspects. It is a combination of the personal and the corporate.
When it comes to church planting, a definite sense of call is necessary. Without a sense of call, working a 9 to 5er will seem much more appealing.