Hey all,
I've just learned that reading contracts thoroughly can make things easier the hard way.
All I had to do was mine 1200 Ore on Minmus and land it back on Kerbin. By land, they mean land, not splashdown... So, as my contract did not register, I put together a (particularly) ugly seaplane and dragged the precious payload back to KSC. Today I've sailed 45km through Kerbin's ocean at 20m/s just to bring back a juicy amount of funds... and that was worth it, because it paid for permanent mining outposts on both Mun and Minmus, both associated with orbital fuel depots, equipped with lightweight landers for wealthy tourists. Those investments will pay very soon...