@Erica17, this raises all kinds of red flags for me. Especially as scammers are known to prey on new hosts.
Firstly, the guy won't just be crashing on your couch, but sharing every other inch of your living space as well (with the exception of strict private areas). He'd end up being virtually a room-mate.
Secondly, in CA a guest staying longer than - I believe - 30 days, can automatically claim tenancy rights, often leading to long and horrible legal procedures to get the person evicted. I note that this guy wants to stay for a month. And yes, a weird way to spend a business trip/vacation. If it's business, for example, his firm would be paying for a room or a suite.
In your shoes, I would decline the request, indicating that your accommodation is not a good match for his requirements. Full stop.
As as others have suggested, I also strongly urge you to create a comprehense, clear, and firm set of House Rules.