Purchase extra passenger cabins, then go to the bulletin board and accept passengers. Try to buy another ship. It will be refused, but the difference in price between your ships will be given to you -- try buying a cheaper ship.
Start at Sol and sell all your equipment except for the nav computer, auto-pilot, and atmospheric shielding. Buy enough fuel units to reach Bernard's Star. Fill the remaining cargo space with luxury goods. Fly to Bernard's Star and go to a station (Miller Depot). Sell all the cargo and buy enough fuel units to return to Sol. Fill the remaining cargo space with robots or computers. Return to Sol and sell the cargo for a large profit by finding special buyers on the bulletin board. Repeat this route to build your profit.