Note: I’m only done this with Tailscale. I have not looked into this with headscale.

You can invite them to your network, or share a machine to their network. The second option is probably more likely what you will do with Tailscale since it is unlimited and the first option has a limited number of users for the free tier. The biggest hurdle will be them getting devices added to their tailnet so those devices can access your machine.

I imagine it’s maybe a little easier with headscale. I haven’t gone down that route yet. I would probably want to have my DDNS point to a VPS and have that be the entry point to my network. I could point it to my ISP IP, but one more layer that isn’t very expensive is probably smarter security wise.