We recommend to ask for a rent which doesn't exceed your own costs, so that you don't make a profit from the sub-lease.
But of course you can demand a sum that covers your effective costs. That includes ancillary costs, such as utilities (electricity and water), TV and radio license fee, internet charges, etc, in addition to the gross base rent.
In theory, you could also apply a surcharge for the furnishings, but this is seldom done in practice because as a private subletter, one's primary objective is to cover, or at least substantially minimize, one's effective rental costs at home during an extended stay abroad.
The fact is that the majority of our providers demand only their effective costs and about a third even less than that. Only a few ask for a surcharge for furnishings.
We don't publish clearly overpriced apartments.
When setting the rent, you must also observe the rental brake/rental cap (Mietpreisbremse §§ 556d ff. BGB). It does not apply in the case of renting residential space "for temporary use" and if the tenants do not form their centre of life in the rented flat. However, since such tenancies are usually only very short-term and thus usually fall under the misappropriation law that applies in many cities, we specialise in longer-term tenancies (usually from 3 months). If you now make a rent surcharge that is too high, the rent you charge could be higher than the maximum 10% above the local comparable rent stipulated in the rental brake/rental cap. For this reason, too, we recommend that you only charge your own costs and do not make a surcharge.
No responsibility is taken for the correctness of this information.