There are lots of ads on info boards in the Mensa building, offering flats to share. This is called “WG” or “Wohngemeinschaft”, i.e., you get your own room but share kitchen and bathroom. The rent for this kind of accommodation is usually quite low.
If you rent an apartment make sure the deposit is reasonable: i.e. two or three monthly rents. Kaltmiete (rent excl. heating and service charges) and Warmmiete (rent incl. heating) refer to the amount of the basic rent and the rent with utilities. The deposit is returned to you with interest if you leave the apartment undamaged. The landlord should set up a deposit account with the bank for this purpose.
is directly paid to the electricity company with which you sign a contract when moving in. Since they can only estimate how much you will consume, you pay a monthly flat rate and the difference is settled after the end of each year. When you move in and out, and also sometimes in between your tenancy, the electricity readings are taken by them. If your consumption exceeds the payments made so far, the monthly flat rate will be increased, if you have consumed less, it will be decreased. In some houses the hot water is heated by a boiler instead of the heating system and hence uses electricity. Please note that this increases the costs for electricity immensely.
Besides the monthly electricity charges, you are charged for utilities, which include the costs for heating (including heating up the water if not done electrically), garbage disposal, property tax, charges for street cleaning, lighting in the public areas of the house, costs for the elevator, water consumption and sewage, fees for the janitor ("Hausmeister"), insurances, cable tv, and for tending the garden. The utilities ("Nebenkosten") account for the difference between the "Kaltmiete (basic rent)" and the "Warmmiete (basic rent plus utilities)".
The biggest portion of the utilities is caused by heating costs, which very much depend on your consumption (not only heating up your room but also heating the water you consume (shower, etc.). When moving in and out, the meters for the heating and water are read to calculate your consumption during your tenancy. All other utility charges are calculated according to your length of tenancy and number of square meter of your flat.
If a fixed utilities rate ("Nebenkostenpauschale") has been agreed upon, it is not calculated at the end of tenancy. If a flat rate for the utilities is agreed upon "Nebenkostenvorauszahlung"), the utilities will be settled against your monthly payment. Together with the final bill, which may be sent to you up to a year after you move out (it takes so long because the owner waits until he gets the final bill for his house/flat in spring for the previous year), the landlord has to enclose all invoices/receipts for your information but may ask for a refund of the expenses for copying these papers.
Please note that utility (especially heating) and electricity charges are raised every year due to the increase in prices. This affects all of Germany and is often like a 2nd rent since sometimes they are as high as the basic rent ("Kaltmiete"). Therefore, do not underestimate the importance of saving energy by switching off the heating when leaving or airing the room, not overheating the rooms but wearing a pullover inside the flat in winter instead of only a t-shirt and not wasting water (especially hot water), etc.
Before you sign the lease, ask a German native speaker to go through the main paragraphs with you. Do pay special attention to the paragraphs added by typewriter/handwriting. Please keep one copy for your records (needed for the local Citizens Office). We also recommend writing a complete list with the landlord which should document all pieces of furniture in the apartment and, more importantly, any damage you notice, even if only minor. This helps to avoid arguments over money with the landlord when moving out.