Bear in mind that your cargo is not insured, it's easy to loose between 1 and almost 7 mil credits on goods alone if you are flying a trader class ship and get interdicted and destroyed.
If you are light on credits, it could be a safer bet to take smaller loads, reducing your exposure to risk till you have built up a buffer of credits to fall back on in the event of annihilation.
Never eat into your insurance fund and risk loosing your ship. If you get destroyed and loose your insurance fund that way, take a free sidewinder and store your trader ship, then grind enough credits to cover your insurance before resuming.