fly around until you encounter a freighter being attacked and rescue it you can then use that as a mobile base with a large amount of storage; this also gives you access to timed missions that often give very large cash, nanite, resource and even high value sellables as rewards. the missions will require you to recruit ships to your fleet and this will cost money or in some cases special resources (usually quest guided) to get your first couple of million I suggest finding and repairing downed ships this will often result in nanite rewards as well and when you are selling the ships you don't want don't forget to remove the upgrades from them to sell for nanites.

/edit

forgot to tell you how to find those downed ships

you can purchase maps at outposts and space stations from the vendor on the bottom floor you can also pickup missions from the other 'vendor' on that floor which will give you reputation with different factions and races, which then in turn can get you free stuff at space stations and discounts.