How many credits should I save up before buying a carrier?

Ive heard a lot of people say 7bil is a good mark. I personally want to use my carrier as a mini station for when im heading out in the black – finding my own sights instead of looking them up somewhere. And for that case you dont really need a lot of services. If im correct only refuel, (repair (I have repair limpets on me I could switch from ship to ship, would I still beed this service then?)), (Armoury (depends on what this does, I cant find any info on it anywhere (even on the wiki) but I guess it would be advanced maintenance?)), cartopcraphics, and vista. Even if I end up needing all of those services that would still only add up to around 5.5bil credits buy price and 12.8mil weekly upkeep which I can easily make within a week of exploration. My condas rebuy also isnt extremely high (13.9mil) and I never even had to rebuy a ship more expensive than 5mil. I though maybe aiming for 6bil would be reasonable since I have been grinding robigo sothis missions for the last few days and i cant stand it anymore xD A lot of people say you should just play the game at your own pace and buy a carrier when you have enough credits instead of grinding for one, but after over 700h of gameplay i still havent even made a billion through exploration (which as of now is the only thing ive ever really done)… Earning my carrier this way would take way to long and again, having my own station out with me would give the exploring a whole new perspective. I guess im just asking you to let me know if im right with the whole services stuff and if 6bil really is enough for what I plan on doing, I really cant do this much longer ._. (im currently sitting at 4.4bil btw)