this. As soon as you can afford the stock Cobra, go for it. It's much better than the (stock) sidewinder, has more cargo space, bigger shields etc without an upgrade.
Use it for trading and upgrade your bits and bobs as appropriate - remember to sell your hardware before your ship, as hardware keeps it's original price (you never lose out on selling equipment) but your ship devalues by 10%. If you sell your ship with hardware fitted, you lose 10% of the hardware value. you'll soon make the money back for the ship and can start specialising in your area of choice!
Right on, Commander, fly safe o7