When running a commercial "hacker space" you have a ton of problems with strangers, it sounds like you're focused on a community hacker space which can be much smaller scale with fewer rando issues. I was on the board of a successful commercial/community hacker space for a while and our problems were not around money (we had a great community of paying members who also volunteered to maintain the space) but more people not using the space in ways that were acceptable to the community (mentally ill members trying to live there, people doing stinky projects, people abusing the tools, major disagreements about how to organize scrap wood, plumb the dust collection, etc). You probably want to avoid this complexity (at least, for now, until you start running into scaling limits) and stick to the "computer club" community.
You will probably want an onboarding process with liability waiver. This is partly materials for parents to help them understand what their kids will be up to at your house. You're going to host other people in your place and there is liability that comes along with that.
You will need to figure out how to keep your computer club from devolving into a lan party (unless that's what you want) and focused on learning opportunities by providing guided learning opportunities. LLMs are really good for helping you develop these activities based on an idea, including digging down into the details. Some things that kids might be into: building adder circuits in Minecraft with redstone (requires a basis in binary math and logic gates, which you can teach on paper and in minecraft). Scratch programs to fulfill certain goals (build a gravity model and get a spaceship to orbit; make a clone of a simple platformer video game they like; etc).
After you have some ideas for projects/classes, you're going to want to write up a schedule so parents can help their kids get there. You should also provide volunteer opportunities so kids (and possibly their parents) can help out - maintain the website, fix the computers, etc. This not only helps lessen your workload, it also gives them a sense of community, that they're not just coming to hang out, they're responsible. Make sure to have community standards around cleaning up after yourself and enforce them.
So, maybe after having a couple of scheduled classes, put out a call for donation of old computer hardware, and maybe have the kids try to assemble some working systems from whatever you get. Good luck!