Such jobs would not only be tedious but also mindbogglingly boring. I suggest the gold income should be proportional to the difficulty level such that in harder difficulties you earn greator amounts of gold for the same tasks. I still think the best way would be to get gold by killing creeps...the higher the level of the creep the more the gold. That would keep the motivation for killing every creep in the level and should make the game much more fun to play with. And i beleive you could change the fixed price of some objects. Say create a trading object like grain sack or jewellery or whatever. Some shops should sell at more value and some shops at less so you can incur profit or loss selling different items at different places. You could make a new skill called trader that would help the player get profit.