I recently started a fresh account, and the answer is... Core mining. Unlike the high paying passenger or haulage missions, it does not require any reputation or a large ship. All you need is a ship width a DSS for finding hotspots, a pulse wave scanner (utility Slot) for finding the right asteroids, a seismic charge launcher and abrasion blaster (weapon slots), and the standard mining internals - prospector limpet controller, refinery and cargo space (collection limpet controllers are a bonus). You do NOT need tons of cargo space. The new core materials sell for ~ 400k - 1.5mcr per ton. Even if you crack every Core asteroid you find (not just focus on VO or LTDs) a small ship with a 40t capacity will net you at least 16mcr in one run.