I was just thinking about who God uses & how He uses them. In the beginning of the church, none of the church planters had set out to be church planters, because the church was brand-new. Peter (among others) was first a fisherman, & Jesus called him to give it up & follow Him; this was the general pattern with the 12 disciples. Paul, on the other hand, made tents, & it is said in Acts that even as a traveling church planter he still made tents; that is, in fact, how he made some of his contacts. In the same way Luke, as a doctor, traveled with Paul & others, but I'm under the impression he was still a doctor ("doctor" or "physician" may have been different back then from how it's considered today, but that's beside the point).
Today God has blessed us with many preachers & missionaries, many of whom did other things first, & many of whom went straight into vocational ministry. My dad, for example, was a computer programmer who gave up being a computer programmer to go into the ministry. Just as much, though, God uses people who have various occupations-- who also know His Word-- to serve Him in the local church as lay people. Any kind of ministry that is effective is completely by the grace of God, & He can use anyone, & He will put the people who follow His will whom He has chosen where they need to be, doing what they need to be doing, to bear fruit for Him. Today I am an office assistant in a Legal Office in Columbus, Ohio. Maybe God wants me to do something else someday, or maybe He wants me to stay here, but in either case I know He will use me. If you know Jesus as your Savior, & are studying God's Word as your authority, & are willing to do what God wants you to do, God will use you no matter how pointless you feel your occupation is!