After dumping into the fleet carrier bank enough credits for +15 years I haven't even thought about maintance fees for several years.
I made most of that from exobiology in deep space. Since then most of my billions came from Thargoid war activities.
IMO the best way to make credits is by simply doing whatever activity you want to focus on, and the credits will start to pile up. I made several billion doing PP 2.0 activities. Unfortunately the direct action of making a colony doesn't make credits. Perhaps surrounding activities can, like selling commodities to other cmdr carriers. Or selling stuff from your carrier.
I made most of that from exobiology in deep space. Since then most of my billions came from Thargoid war activities.
IMO the best way to make credits is by simply doing whatever activity you want to focus on, and the credits will start to pile up. I made several billion doing PP 2.0 activities. Unfortunately the direct action of making a colony doesn't make credits. Perhaps surrounding activities can, like selling commodities to other cmdr carriers. Or selling stuff from your carrier.