Legal Question in Real Estate Law in California

It depends on what the sublisting agreement provides. If it only says that you are authorizing the tenant to list the property for sub-lease and that the sublease is authorized under the master lease, that's fine. If it makes the realtor your agent and/or obligates you to a commission, however, you have no obligation to agree to that.

Legally, you would have to agree to subleasing, depending on the terms of the original lease agreement. For example, if the original lease contained a provision prohibiting subleasing, this would have to be modified by all the parties, in writing based on typical lease terms.

Whether these subtenants are a good idea is another matter altogether.

I take it that the proposed agreement is with the tenants' agent, not the agent for some particular subtenant. If so, the request seems reasonable, but you should read it rather carefully before signing, to see exactly what you're agreeing to. If it only says that you consent to the concept of a sublease (actually, it's probably an assignment, since it is for the remainder of the lease term), that should be fine. If you are agreeing to pay a commission, or indemnifying someone, maybe not so fine. You should retain some right to interview and approve, or diapprove for cause, any subtenant they bring in for approval.