Legal Question in Real Estate Law in California

Re: defaulting on a lease before moving in

It doesn't sound like you have any damages for breach of contract, since a replacement tenant has signed on. There's no sense in trying to enforce the provision of the lease when you've incurred no damages. Good Luck.

Re: defaulting on a lease before moving in

The lease was effectively breached when the original cotenant repudiated it.

At that point you began to accrue damages. However, by law, a landlord's right to damages is subject to an obligation to make reasonable efforts to mitigate (limit) those damages. This you did, by accepting a substitute cotenant.

You could in theory sue the breaching cotenant for any losses you incur due to a short gap between when rent would have started to flow and when it actually will flow to you, if any, plus any actual out-of-pocket costs to you to bring in the replacement cotenant.

You cannot, however, sue the breaching cotenant for three months' rent. If you were allowed to do this, you would be exacting a penalty, not getting reimbursed for damages. The law doesn't allow private parties to charge penalties for breach of contract; the parties can contract for reasonable liquidated damages instead of actual damages, but never for a sum that amounts to a penalty because it's out of proportion to actual damages.