Anyone who is a pastor/minister should be gently directing the flock, as a shepherd does with the sheep. Two scriptural passages clearly state this. “Be shepherds of God's flock that is under your care, serving as overseers-not because you must, but because you are willing, as God wants you to be; not greedy for money, but eager to serve; 3 not lording it over those entrusted to you, but being examples to the flock.” (1 Peter 5:2-3) “Jesus called them together and said, ‘You know that the rulers of the Gentiles lord it over them, and their high officials exercise authority over them. Not so with you. Instead, “whoever wants to become great among you must be your servant.” (Matthew 20:25-26)
People who function as pastors of churches can work other jobs, as many do. The Apostle Paul earned his living by tent-making (Acts 18:3). It all depends upon the church and the situation. Large established congregations may desire their pastors to be involved in many things that would preclude them from having an additional outside job. These might include, but are not limited to: visiting congregation members in the hospital or nursing homes, preparing and carrying out teen activities, preparing and conducting Bible studies in addition to the service on Sunday, sitting on committees that interest the congregation, counseling congregants—pre-marriage, marital, individual, etc. As you can see, with all these duties/activities, it could be very difficult for the minister to have an outside job.
There are other Christian congregations that have voluntary or minimally-paid ministers. These pastors, by necessity, have outside jobs, either full or part-time. Then in their “free” time, they work to serve the needs of the church, writing sermons, maybe counseling people, trying to keep in touch with ill congregants, etc., balancing this with the needs of their family, if they are married.
Tithing is an Old Testament concept. The tithe was a requirement of the Law in which the Israelites were to give 10% of the crops they grew and the livestock they raised to support the tabernacle/temple and those who worked in its service (Leviticus 27:30, Numbers 18:26, Deuteronomy 14:22-23, 2 Chronicles 31:5-6). Since the days of Jesus’ ministry, some churches have “borrowed” the concept of tithing as a guideline for what members of congregations should give to support the church and its ministry. Others have not. The New Testament does not mention tithing, but talks about the importance and benefits of giving. 2 Corinthians 9:7-9 tells us that we should give willingly, as our heart directs us. I Corinthians 16:1-2 tells us to set aside some money according to our financial prosperity for those in need. Today’s church practices on giving vary widely. Some are militant about tithing—some even demand double-tithing (20%). Most suggest it as a guideline, and others merely urge generous giving. The New Testament does not seem to authorize anything more specific.