Tips for finding cheap apartments, average rents in every part of Berlin:

• http://berlincheap.com/cheap-flat-berlin/

Selling cheap second-hand products, or sharing them for free (e.g. furniture, bicycle, television) is very common in Berlin, and usually a better option than buying everything new.

• At TU Berlin: http://ula.blogsport.de/

• Popular Facebook group for free things, also containing many BMS members: https://www.facebook.com/groups/freeyourstuff/

• Online about any kind of products: https://www.ebay-kleinanzeigen.de 

• Also online about furniture: http://berlincheap.com/category/furniture/