Short-term rentals in Germany can be difficult to find and will often fall on the corporate end of things, i.e. renting to companies who want to put up executives and are prepared to pay a premium to do that. Standard rentals in Germany also don't come furnished - you quite literally need to bring the kitchen sink with you (or sometimes you can arrange to buy the kitchen from whoever is leaving). It's not impossible and AirBnB might be some help. Or else I'd try something like
http://www.wg-gesucht.de/ - a WG is a Wohngemeinschaft or houseshare. That way you mightn't have to buy more than a bed. Bear in mind I've been feeling very complainypants recently so you'll need to counter this with some of your own optimism (but stay realistic) - these are some of the other expenses you should take into account if you want to live in Germany:
- Health insurance, compulsory for everyone who is resident in Germany, even temporarily and many international plans are not valid in Germany. Travel insurance will not cover this.
- Television licence equivalent, since 2013 compulsory for each household (whether you have a telly or not) so if you get a room in a houseshare, might already be covered.
- Third-party liability insurance (Haftpflichtversicherung) and household insruance (Hausratversicherung) - you'll probably get away with not needing these but my rental contract, for example, made having these insurances a condition of rental so I'm just mentioning them as you might come across it.
- Mobile phones are ridiculously expensive here (IMO) but there are lots of cheapie pre-paid plans available although coverage can sometimes be an issue. I currently use Edeka (one of the supermarket chains) and find it reasonable - hope to get a smartphone soon and got this because they have what seems like a decent data plan (8.95/30 day for 300 minutes to any network, free to Edeka network and 300MB data or 9.95/30 days for 500MB data) that I can easily add and because it utilises the 02 network.
- On a less negative note, beer often costs less or the same as water when you go to the pub so, there's that. :)
Cost of living can also vary quite a bit depending on where you live so if you know exactly where you want to go and can give some indication of where it is, we could probably give a better idea of what to expect. There are lots of general tips that will apply everywhere, like finding your local Turkish supermarket to get lots of staples for less instead of just going to the mainstream supermarkets.
Also, can you speak German? That'll totally change your experience and, you know, I'm just nosy and want to know.
There's a website with extensive discussion forums for English-speaking ex-pats living in Germany that is a great source of information for anything you might need to know about living in Germany (just
do search before asking, they come down pretty hard on people who don't check first, since most questions have been asked and answered before):
http://www.toytowngermany.com/