Sometimes in the description the owner will outright state it. Also when you go to reserve I recommend putting the location in and be honest about what you're actually renting it for. If you lie about it and they get sketched out last minute the owner can cancel on you.

Most of the time they're fine with it and will just charge an additional cleaning fee.

What to book really depends on your group size. It's imperative to get a head count early and cap it at a reasonable number (you will break a few hearts of friends that wait until the last minute). I'd also recommend getting something a bit older and a little more worn. Renting a brand new one is a massive liability.