People are not going to pay to play in your server when they can play in another for free. There will be little people in yours, so it isn't like there is some amazing 20 player TDM with a bunch of huge spaceships and lasers flying everywhere.
hink about it like this, people subscribe to games like runescape and WoW because it is a full game with lots of people on it. Subscribing just to play in your server is stupid, as every other server can do what yours does but for free.
Forcing people to pay to play on it will just lead to your server having 0 players all the time.
Also, your computer repair thing? You will face so many legal problems with that about people sending in their stuff and you not knowing how to fix it, and they wasted their money on your service.