Having grown up as a missionary kid in the Amazon jungle of Venezuela, I know well how much a church can bless a missionary family by their giving. When churches gave money, we were blessed because our needs for food and clothing were met. The church would feel blessed hearing our grattitude and knowing that they had helped further the gospel in the indian tribes by supplying our needs through Christ. Sometimes, the churches would send small groups of people down to help our. Sometimes they would build small church buildings, sometimes they would build small dispensaries (it is hard to witness to tribal people unless you can provide the medications to bring them through their illnesses.) Regardless of what was given, we always wrote home and told them about the progress of the ministry, people who had been saved, now saved indians who were going out and ministering to other tribes, etc. The churches knew then that they had been a part of this great work, and that without their help, it could not have been done nearly as quickly.
Most foreign missionaries cannot work for themselves. Their lives are fully dedicated to furthering the gospel and they rely on others to supply their needs. That is a hard spot to be in, but they do it anyway because they know that God will be with them every step of the way.