Puzzle

I had been a Christian for a long time. Being a person who had little or no social activities, I have lots of times to ponder and think about things. Things that concerned about religion, philosophy and logic thinking always popped into my mind. However not all question I've taken them seriously, some just comes or ignore, others left their imprints in me.I guess that happened when you have lots of free time and don't know what to do. One of these question are about offering and cross. 

In my christian life, I had attended many services and missed many of it too. But one things I notice it the service during Sabath day run routinely. there is always the prayers, then the worship- singing hymn which followed by offering collecting and finally sermon. After sermon prayer is prayed before everyone leave. When it time for offering, I had always wonder how the money is used. Some church I know, do charity work and community work that require lots of money to do, but how about those churches that has does not involved in such activities. I had heard that some people who opt for full time ministering or missionary are being paid by the church. It is very noble and faithful to do so but should they been paid for it? I mean minister in biblical time never receive salary.They earn the money themselves. I mean Paul is a tent maker, the twelve disciple are fishermen, even Jesus, son of god is a carpenter. So why nowadays some people get paid for ministering? 

Some other thing bother me also. the cross that had been placed in worshiping hall in some churches. I have read the tenth commandment. one of the commandments clearly said no idolatry. Some people said the cross is to remind them about salvation and Jesus died to save our sin. Yes it is not wrong to remembered Jesus death save us. But can't it be done other way, taking the Holy Communion for example? Isn't praying, singing in from of the cross consider idolatry?