An AspX can get you a decent path to making money doing various missions, but ya that's not even counting the outfitting of those ships aside from modules that can be shared.
The problem is more in the end game it seems, seeing a lot of missions that require 3000+ units delivered for a mear 2.5 mil payout, meaning you'd have to do a lot if you went with the Type 9 for the storage capacity. Vs the 400 or so you get on an Anaconda. Just to get your money back.
Those 3000+ cargo missions are not that fun, and have lock what fine you will have to pay if you fail those..
I look for the missions that will have you to fetch something, they pay alot higher, and that is for a reason, you have to also pay for the cargo....and the wing versions of these are the best....
The second problem with those missions are that most of the time, the really good paying ones, requires cargo that is hard to get, so check availability before accepting.
For example, lets say you find a mission to get and deliver 1620 slaves and for that trouble we will pay you 32 million....
So checking out availability, you will soon discover that we have two kinds of slaves....
Imperial Slaves - easy to get, I wonder why that is
Slaves - A much rarer form of slaves..
Buying 1620 slaves will set you back ~18 million credits, making your profit to be only be 14 million... And even in a Type 9 or Cutter, you will be making 3 trips if you do it solo... and I guess you will have to travel 150-200 LY x2 for each delivery (unless you are very lucky)...
So you do this solo, and can now cash in 14 million
But if you wing up and share it with your friends when turning the mission in, they will each get 32 million for your hard work. So in this case, free credits for your friends. Credits that would otherwise just get "lost"
Now if your friends spotted a similar mission, and they did those solo and share them before they turned those mission in, now you get the full 32 million for their hard work!
And if you decide to make this a team effort, and you are 4 in the group, and you share the cost to buy all the cargo (slaves), then
You have to pay 18/4 = 4.5 million per player
And you will each make 32-4.5= 27.5 million when mission is completed.
So these can be very lucrative wing cargo missions, but be vary about some stuff that are requested can be a pain to get....
And most of time doable solo. But the real trick is to share it before completing the mission, as that is FREE credits.
Of course this last part sucks for the solo only players, but this is after all wing content, and they are doable solo too.
And for combat related wing mission they work mostly the same, but they most of the time harder to complete for the average solo player, so here doing them together as a groups is recommended. I recommend the Kill Pirate Lord, these can be alot of fun, and for the average player a good challenge. And with practice, better equipment etc, you will do these faster and have less (no) lost ships... There is no shame in making a tactical retreat and try again.