No tuition fee but the student body and social contribution fee needs to be paid each semester (more details). There is no extra application fee.
The German Research School for Simulation Sciences does not provide funding for Master's students. You may, however, try yourself to obtain an independent scholarship. Some useful information you can find here.
Once you are enrolled as Master's student you have the possibility to look for a job as student research assistant (HiWi) at one of the laboratories of the German Research School or at any institute at RWTH Aachen University. A typical HiWi job means to work for 10 hours a week in one of these groups and is remunerated with about 400 Euros.
The living costs at Aachen are roughly 700-900 Euro per month, please see also here. You might find some more interesting information on the web pages of Studentenwerk Aachen.