2 Thief with level 8 thievery (+3 from unique top, any belt and any hand) is almost 30k per npcs. 15k if you only steal once.
Lucky charm saves money.
Always sell old gear (except maybe unique, keep them in your chest) and get good barter. You only really need barter at level 4-5 with gears since it doesn't scale that well.
Money shouldn't be an issue after that as its usage really drops starting in Nameless Isle with most legendaries and divine completely disappearing for certain type of gears. Act 2 is where you need the most money but that's also why it has the most trader as well. Every region of the map has at least 3-4 people you can steal from as long as you don't turn in their quests too fast (like Eithe).
