Legal Question in Landlord & Tenant Law in California

Such an agreement is worth little, as it is an agreement between you and the renter and does not bind third parties. At best, it means that if you are sued then he would have to reimburse you, but if he is a renter he probably does not have many assets or any that you can go against, so the attempt at an indemnification clause ha little value unless you can force him to get a renter's liability insurance policy. If someone is injured, their attorney will sue everyone who might have some legal responsibility; as owner of the property, you are the most obvious "deep pockets" defendant since it is assumed you will be carrying substantial liability insurance, which you should. Even if you have absolutely no fault [fight breaks out and plaintiff hit by another party goer], you likely will be sued and it will cost several thousands just to get out of the case [but your insurance will defend you for free on any negligence claim].

Having the agreement might have a positive psychological effect on the renter. With a hundred people there, there is a high risk of someone getting injured. You could ban such large parties. Insurance is your only sure protection.

not proof read

Mr. Shers is correct. An agreement between you and the renter could be legally binding between the two of you as to who pays a judgment, but not binding on the injured party, and if the renter doesn't have the assets to pay, your agreement will be worthless. You need to make sure your insurance is up to date and provides adequate coverage. I would also recommend that you require your renter to have renters insurance and that they provide you proof of insurance paid up to date before each such party. That's the best protection you can get.