418. Liability may usually be determined by agreement.

In certain cases, a landlord may be debarred by statute from shifting a cost burden which the legislature has imposed upon him to the tenant1; but in general, where a tax or rent is prima facie to be borne by one party, it is competent for the parties to agree that it is to be borne by the other party2. Thus, while certain improvement expenses incurred by local authorities and expenses in connection with the abatement of nuisances3, if recovered from the occupier, may be deducted from rent, in each case the right of the occupier to deduct the