Modesty my friend, you can't expect to constantly afford the best armor with the best sword with the heaviest xbow.
Basically there are two methods, first one is to keep your equipment cost down to a reasonable level, most players break even at about 50 k (I use roughly 30 k worth of gear as inf), second one is to have different sets of equipment, one just for farming gold. (I would advice against this as it gives a much more "grindy" feeling to the game imo).
Upkeep is there for a reason, otherwise evryone would just walk around in plate 24/7