Running Cargo in Star Citizen 3.0 is lucrative.

Star Citizen 3.0 is in it's first patch 3.0.01, The Game continues to become smoother ans less buggy with every passing month now. The Star Citizen Team is hard art work for the next level 3.1. But has not abandoned honing and perfecting this now foundational building block that will become an expansive universe. In this very first level of what will be the actual game cargo was introduced, Four Planets you can land on and explore and numerous missions that change. The missions offer a minimal amount of in game credits but for the people with ships that have cargo room, it's a credit making machine. The mechanics of trading still apply. Buy low and sell high. The mission offer a way to regain buy money should your ship fall under attack and you lose all of your credits by getting destroyed. 

A freelancer offers 66 SCU cargo space, so it doesn't take too long to amass credits in the 6 and 7 digits. The economy changes from time to time, but the well established Port Olisar offers the highest prices and is pretty much official the selling hub. It takes a little travel and math to so figure out how to optimize your profit since every haul is indeed a risk. Nothing that a notepad and pen won't take care of.

There are several mining posts on the planets from ARC CORP to smaller seemingly privately owned mining operations. These are prime for the lowest prices. Not all types of cargo can be sold everywhere. Some types of cargo are illegal and better off being sold at Grimm Hex the outlaw outpost near Yella. 

Besides just buying and selling cargo, there are other ways to boost your profits while doing missions. Some missions take you to crash sites either in space or off planet in which the player must locate a deceased, black box, or precious cargo box. But strewn all around these crash sites is often other valuable cargo that can be sold at market. In most cases enough that the credits ad up to much more than the mission itself. But timing is a factor. Dally too long and the mission will end without your completion. But it's worth trying to gather as much as possible at least then your not left high and dry for the time should you not make the time limit on the mission.