@Carla55 I have an entire home listing and I do not use a contract. The only time you need a contract is for Long Term Stays of 30 days or more. Since you are in California, you might not want to do Long Term Stays since after 30 days the guest develops tenancy rights. You should read this link:
https://www.airbnb.com/help/article/805/what-are-some-things-i-should-consider-before-hosting-long-t...
My maximum stay is 21 nights.
Basically your House Rules consitute the contract with the guest. I ask that guests read and accept them before I confirm their reservation request. Obviously I do not have Instant Book turned on.
Hope this helps!