Flexible shifts hiring in Portland - any advice?

A cleaning company is taking applications for evening crews. There are 10 people counting on me, so I am trying to be careful. Shifts are four to six hours and the pay is weekly. Is the schedule really fixed?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.

Check how they treat part-time staff for benefits. Some add them after a set number of hours.