In a nutshell: Early, not to say very early! For both tenants and landlords, it is recommended that the lease be checked in advance by a lawyer specializing in tenancy law. Any questions can thus be clarified early on, potential later points of contention can be "defused" and the particularities of the individual case may be included accordingly in the contract. Experience has shown that in practice, too, there are often disputes between tenants and landlords, because the frequently used model leases, which are available on relevant websites for free download, for the specific case, not fit properly and may be material for the parties Leave points unregulated. Not infrequently, time- and cost-intensive lawsuits are the result. Anyone who seeks advice from a tenant lawyer at an early stage can save money on the bottom line!