Before posting this, I did a quick search on "Wifi" and though I found several of the resulting discussions insightful, I didn't necessarily see anything that would overlap very much with this, so here goes.
This is the story of the evolution of how I offer wifi to guests, shared with the AirBnB host community in case othes have had to overcome challenges similar to mine.
IN THE BEGINNING, I had 1 router and it broadcast 2 wifi networks, 1 for guests, and 1 for me. The guest network was set up to prevent connected devices from seeing each other, as well as from accessing the router's administative interface. The other network (mine) was unrestricted. "In the beginning", I figured that was enough. The unrestricted network was intended to be used by the PS3 I had set up for guests (to use streaming services and the like), but my co-host at the time was uncomfortable with showing guests how to use the PS3, so it was temporarily retired.
A few months into hosting, I get a notice from my internet service provider (ISP) that they are required by law to forward me an email they received from the law firm representing the interests of a content owner whose intellectual property was observed to be downloaded unlawfully from an IP address that had been assigned to my internet account at the time of the download.
I was a bit taken aback, but when I dug into it, I noticed the time and date provided for the alleged violation were while I had a guest at the house (and only the guest was occuping the house at the time).
I considered what my options were in terms of how to prevent this from happening again. My first thought was "Can I set something up that prevents so-called illegal downloading?" Five minutes of research on the matter led me to the conclusion that someone who wants to download, legally or otherwise, will find a way no matter what - the tech and techniques are designed for that. I then considered putting a splash screen up for guests connecting to wifi with some sort of disclaimer for them to agree to, but that screamed to me of guest-unfriendliness. So my next question was "Well, allright, then is there a way I can avoid being targetted by these ISP notices if a guest should do something like this again?" and the answer (after another 5 minutes of research) was VPN.
So I signed up for a VPN service, and then set up my router to stay connected to the VPN. Problem solved, right? Not exactly. In terms of preventing notices from ISPs, I haven't gotten a single one since. Yay! But.
But.
Eventually, I was able to replace some things in the house (including my PS3-unfriendly co-host) and set things up to include a large flatscreen SmartTV, and the PS3 on another (not-smart) TV. But with the VPN in place, some of the more well known streaming services ceased to work (from either the SmartTV or the PS3). Ugh. 5 more minutes or researched revealed that these services actually hate VPNs and make a point of being incompatible with VPNs.
Based on that, one thought I had was to make the VPN apply only to the guest Wifi, and then connect the PS3 and the SmartTV to the unrestricted Wifi, but I could not find a way to make the router put VPN on only one of the wifi networks - it was all or nothing.
So, enter... a new, second router (with no VPN). I connected this new, second router directly to the ISP modem, and then connected my original router (the one with the VPN and the guest wifi) into the new, second router. On the new, second router I set up an exclusive wifi for just the PS3 and the SmartTV. So now they could stream happily with no restrictions. Guests would still connnect their own devices to the guest wifi (with the VPN), so whatever their activities were, it wouldn't result in warnings to me.
Not sure if any other hosts are faced with any of those considerations, but if so, hopefully my efforts will help you, OR, maybe you have a solution already that I could learn and benefit from!
All questions or comments are welcome.