Car rental concession

Hall people, so I have searched a lot and found no clear entries. So again….. To make a rental car business first: As already mentioned I have to make a passenger transport ticket and a local customer inspection for the city where I live. So, I know that I need concession now and where do I have to make it? How expensive will the cost me ? If I have received the concession I can start directly with my car ? Are there by the way other e Cost to come to me? I just want to know how expensive me will be. I have an A6 Quattro 3.0Liter driver’s license: for 13 years Leadership certificate : clean No diseases or visual impairment Please ask for helpful answers