Landlords must maintain and repair their rental property in accordance with certain minimum standards. (CC § 1941.) If a landlord refuses to do so, a tenant may arrange for certain repairs and deduct the cost from the next month’s rent. (CC § 1942.)Further, a tenant cannot give up or modify those rights in a lease or rental agreement. (CC § 1942.1.) 

There is one exception to this rule, however: If the tenant specifically agrees to repair and maintain all or part of the property in exchange for lower rent,
the repair-and-deduct rule can be waived. Although in principle this would seem to be a broad exception, it is not broad in practice. 
Judges look to see if the tenant’s promise to keep the premises in repair was really in exchange for lower rent and was not just a way for the landlord to avoid legal responsibilities.
Chances are the tenant’s waiver will be upheld if, in the written lease, a tenant handy with tools agrees to repair or maintain the property in exchange for rent
that’s considerably lower than fair market rent, but not otherwise.Following is an example of a valid clause that could be included in your lease or rental agreement.
EXAMPLE: Tenants agree to be responsible for all routine repairs and maintenance to the premises covered by this lease in exchange for a monthly
rent of $900. This amount is approximate $200 less than the fair market rent for the premises, which is agreed to be $1,100.

All said and done, we advise against this sort of arrangement. For one thing, even if you include this provision, it doesn’t relieve you of your obligation
to the city or county to comply with local housing codes. You retain this obligation even if tenants breach a rental agreement or lease provision requiring
them to maintain the premises in compliance with city and county regulations. In other words, the city and county have no interest in what you and the
tenant agree to but will hold you responsible if there is a code violation problem.

A better approach is this: If you want your tenant to fix up the property, fine, but pay the tenant by the hour or the job for work agreed on in advance. It’s better to pay the tenant separately and collect the regular market rent. That way, if you’re unhappy with the tenant’s work, you can simply fire the tenant and still be entitled to the full rent. If on the other hand, you agree to reduce the rent in exchange for work, you may be stuck for a long time with reduced rent in exchange for the tenant’s poor-quality work.

1942.1.  Any agreement by a lessee of a dwelling waiving or
modifying his rights under Section 1941 or 1942 shall be void as
contrary to public policy with respect to any condition which renders
the premises untenantable, except that the lessor and the lessee may
agree that the lessee shall undertake to improve, repair or maintain
all or stipulated portions of the dwelling as part of the
consideration for rental.
   The lessor and lessee may, if an agreement is in writing, set
forth the provisions of Sections 1941 to 1942.1, inclusive, and
provide that any controversy relating to a condition of the premises
claimed to make them untenantable may by application of either party
be submitted to arbitration, pursuant to the provisions of Title 9
(commencing with Section 1280), Part 3 of the Code of Civil
Procedure, and that the costs of such arbitration shall be
apportioned by the arbitrator between the parties.