Ramen-style about 600€/month (living with a roommate, prepare your own meals -> maybe it could be even lower if don't go out at all, don't buy new clothes, ride a bike instead of public transportation... )

Have your own space, go out sometimes, take cab once in a while... about 1.200€+/month (obviously open end).

Add at least another 130€/month for health insurance.

Unfortunately I don't know about any python gigs but if you are familiar with RoR, let me know... As a freelancer (RoR) you should get something between 300€ - 800€ / day (deepending on your experience).

Update: For Startup-Jbs you might want to check out: http://www.deutsche-startups.de/startups-jobs/stellenangebot... (not only programming and not only Berlin).

Another place would be: http://www.jobisjob.de/berlin/ruby/jobs (Rubyjobs in Berlin)

You might also consider to get an (free) account at www.xing.com (kind of Germanys LinkedIn which is used by many recruiters).

If you would consider/interested in working for a non-profit (including non-profit pay ;-(, please check out www.betterplace.org or www.spenden.de (the later will relaunch soon). They are/will be done with RoR and are sometimes looking for programmers (mostly freelancers). If interested I might be able to help here.