Like @codatory said, I have managed volunteers in the past. There were benefits, but I don’t think our volunteers did much to negate our labor costs, even though it was something that our comms director was always pushing for.
First, you have to have a strategy for getting volunteers. The church I was at considered volunteering to be part of their DNA, people were always being called upon to volunteer, and once a year, time was even set aside during services to sign up. If you already have people who want to volunteer for IT, great! However, if you don’t, I wouldn’t plan around having volunteers yet.
In addition, you need to place your volunteers well into your department. Before they volunteer, I would encourage you to get coffee with them, and gain a better understanding of their skill level and how trustworthy they are.
Finally, from my experience it is important to realize that just like you need to spend a lot of time training a new person who works for you, you will also need to do this with volunteers. You need to acclimate them to your setup, in some cases provide some training and reinforce best practices. You also won’t see them as much as employees, and they will be more likely to call it off if there is something else that comes up. In some cases, you should probably have a way to keep an eye on what they are doing; where I was at, we would usually have them connect their computer to a screen in my office, so I could see what they were doing for training. However, another purpose for that was if I was letting them make administrative changes, I needed to keep an eye on what they were doing (this helped me avoid some “oopsies”) There are exceptions, but volunteers are generally not a good source of solid long term labor. You can easily spend at least as much time showing them the ropes during the beginning of their time with you, as you would spend doing things yourself. If they are college students or people trying to stay busy while looking for a job (which was really common for us) then there might be a limited amount of time when they can be mostly self-sufficient, while volunteering for you. So you might not get a high payoff in time. That being said, working with volunteers was a great way to build community, and my team of volunteers is something I really miss now that I’ve moved to work at a different church.
There are some relatively rare exceptions. My predecessor at the church I am at now was essentially a volunteer. He made a fortune by coming up with a piece of software with two other guys that keeps getting sold from one company to another and doesn’t need to work anymore, so for a while he was working for a dollar a year. However even though he was undoubtedly brilliant, he still didn’t know everything that he probably should have about how to set up and run a church/school environment well. There were some basic things that were missed. And when the school made an administrative change he disagreed with two years ago, he resigned, and left them scrambling to figure out what to do next.
Sorry for the book but essentially what it comes to IMO is I wouldn’t lean too hard on volunteers until you already have a good reliable team in place. Until then, I would focus on building a good community of volunteers (I’ve always felt community is part of what is different about IT Ministries as opposed to IT Departments). When you have a good reliable team that could be used to help negate cost or increase capacity, I would plan for what happens when they leave. For most people, the way volunteers view their post will likely be different from the way paid employees view their post.