The truth is that there is no formula in terms of how gigs are set up. As you journey through your music career, you will encounter all kinds of clients. Some treat you like servants and don't feel like you need to be paid. Some treat you like kings and queens and fawn at your feet! It's pretty crazy. I've had both of these experiences within days. It was a wild ride for my self-esteem.
I found that once I asked myself these questions, it helped me set up some semblance of a routine, even though most of my clients had no idea what they were getting themselves into when they asked me to come in for a gig. These questions helped me set up my own system so I could guide my clients through the process of hiring me for a gig, instead of relying solely on them to come up with fees and invoice deadlines. A great side effect of developing your own system is that it makes your clients visibly more comfortable with your services! They know they can trust you because your system displays the fact that you have experience. You're showing them that you know what you're doing, and you can take care of them and the services they want you to provide.
I really hope this helps those of you who are just getting into this line of work. It was a roller coaster of good and bad experiences before I came up with any of this, so I'm hoping I can save you guys some time, energy, and resources by sharing my own experience. :)