I work in this business and this thread should help new expats to get an impression about Frankfurt area.
A) "cold" rent
1.)The social department had in past to much problems to get their "customers" into flats, so they changed the regulations for socials some months ago. Any social as single gets payed a rent till Protected content per month!!! without secondary costs(Offenbach has 432,50 Euro) This has and still brings a big influence to the market, coz why should a landlord rent to an expat or normal german employee for Protected content a one room flat? Anyway the 1 room apartments in the favourits districts of Westend, Nordened, Bockenheim, Sachsenhausen and now Ostend had mostly the price range of Protected content up by good condition, coz this areas are to less offers for the many singles who like to live there.
For the flats in such areas in size Protected content you should calculate a rent of Protected content per sqm without secondary costs.
2. I would recommend every expat to look at google map. Frankfurt is different to most big cities. West and North from Frankfurt center you are after Protected content still in Frankfurt district. In East after Protected content you are in towndistrict Offenbach and south after 5 kms in town district Neu-Isenburg where the price are less than in Frankfurt district with same distance to center and same value.
3. i often read from expats that the language is a problem. Not really the main site for ad is immobilienscout24 and this site is availbable in english.
4. Most ads are by agents. The fee of an agent is regulated by law -its maximum , by private, 2 months cold rent +VAT of 19% which most agents also want.
5. Other sites, but mostly in german to find flats are immowelt, ebay and different sites which you will find under "Kleinanzeigen" in google.
6. Deposit is mostly 3 cold rents which is maximum allowed by law and mostly requested by contracts.
7. Most landlords do not prefer shortterm rent of less than 1 year.
8.Normal cancellation time of unlimited contracts are 3 month to every monthly end.
B) secondary cost
1. The secondary costs rised up a lot in last years. Standard is, that all costs are included except personal electricity, Internet/telephon, fees for television. Seldom heating is separtaed, sometimes to compare offers you need to look for warmwater if produced by central heating (than in secondary costs) or by electrical heater or boiler(which you pay by your personal electricity bill)
2. IMPORTANT -some agnets and landlords offering - as example - warm for Protected content and in contract is written cold Protected content secondary 50 which is allowed , but not really serious, coz with 50 Euros the costs will not be covered for secondaries and later you need not pay the difference to real consumption.
Let you show the old secondary costs from years before and calculate Protected content % more for actual year.(Take care about consumption of ccm of water for example -not that the previous renter was mostly not there - with Protected content water per year nobody will be able to have shower, washing and so on)
3. Calculate with 3 Euro per sqm secondaries.Influeces are smaller the apartment- higher you need to calculate(not all secondaries are by sqm) and the age of the house (isolation, age of heating system and so on)
C) furnished is not usual except mostly specialiced companies who are offering all inclusive prices for shortterm. IF you rent an unfurnished one -best is to look in ebay and rent a transport car at weekend to get the goods together, also are there every weekend in Frankfurt area "Flohmarkt" where mostly privates selling there used goods.
I hope that this helped some expats and would be happy when some internations memebers writing here there expereinces -also persons from Frankfurt, if i forgot anything or made a mistake.
best regards and good luck by finding