It will be VERY difficult to make a living with a Polaris. The 315 is a good starter ship, but you will need something to pay the bills.
From what understand about the game as it will be (at this point in time), your career will start small and then get big.
From a military stand point, you will need to be able to show skill as someone who can clear out small groups of bandits, and then move on to bigger successes. This means a ship progression that would look more like this:
315/325/Gladius/Hornet->Super Hornet/Sabre/Bucc->Vanguard/Freelancer->Connie Andromeda/Retaliator/Redeemer->Hammerhead->Polaris->Idris->Javelin.
Now, you might not need every ship in that lineup. You might be able to go from a 315 to a SH and then up to a Retaliator/Redeemer and then from there to a Polaris, but you won't get the big paying missions right off the bat. Now, you can probably skip the 315 and Gladius and maybe just go directly to either the SH/Saber/Bucc or the Vanguard, but that's probably as far as you can go and still make money initially. You might be able to make money privately as an escort with something like a Hammerhead or a Polaris, but that will require people to be using Hull D and Hull E ships, which also won't be profitable right away. Now, some might start being used within a week or two of launch, but they will be much fewer and further between and will require the same ability to profit from trading as currently exists (which is probably over rewarding and will be tuned down to string out the timeframe.)
My suggestion is to have a plan to make money while building your reputation. Otherwise, be prepared to be buying a lot of UEC off of CIG for real money while you build your rep to the point you can support yourself in game.