One way or another, I need to be paid for the time and effort I put into projects. How much will a job cost? You'll need to ask me for an estimate or proposal.
I use two ways of charging, to suit different kinds of work:
I do most work for a fixed fee. This suits projects where the client and I agree on the scope of work at the start. I know what has to be done, and my client knows what it will cost. I usually invoice each month for work in progress.
On some projects the scope of work is unpredictable, so the time charge system is the most equitable. This way, I can do just what is needed. My monthly invoices include detailed logs of the time I have spent on the project. I can usually provide broad estimates, or agree upper limits.