Early on, you can use a really "quick" way of making money that does not take much energy or in-game time (although it may take quite a bit of real time). Just enter the Excavation Site and before you do anything further, save your game inside.
Proceed to dig for jewelry but do not save your game again. Instead, simply note the map cells where you found the jewelry by digging up the whole place. Go reload your last save and go directly to the spots where you found the jewelry pieces before and dig only those squares. Save your new found riches, and reset the Excavation Site by exitting and re-entering the map.
You can loop the exploit -- the interred jewelry will randomized upon entry to the Excavation Site (note leaving a mine and then going back won't do; you need to exit completely to the 'outside'). You can repeat this as long as you want (or as long as your dude's energy holds out). While not helpful when other avenues of revenue are available, you will find this quite helpful early on in starting up your place.
