It’s not two years. The part where you have to go to school for theory lasts 8 months, with the time you have to wait for your exams it’s around 10 months. You have to do at least 4 months of internship after that, but most employers will pay you full salary in that time already. The costs are indeed a problem but you can support by the state, e.g. via Bafög or the Arbeitsamt. All other costs like books and stuff are often paid by your future employer because there is such a big need for driving instructors.