in order to get 20k per day u need to bot about 5-20 hours a day ofc the more time u bot the higher chance of ban, where u bot counts too, to get 20k in about 5hour you would need to be botting the most popular dungeons which means a very high chance of ban even if the time is low, 10-20 hours would be world farming and depending on the spot you may run in to a lot of ppl increasing the chance of ban, botting for that many hours also increase chance of ban, i would say that 7 or 8 hours split up in a mid/low pop dungeon/ raid would be best or just go full 24/7 which means you know u will get banned but all ur gold will be safe in a guild bank on an other account that does not bot, guild bank has a small chance to get removed
noramlly ppl that bot for gold to sell do it on an account thats a battlechest aka lvl 90 toons, they know they will get banned and dont care coz it only costs $5 for the account and they can make that back and more within 2 days or less(1st day would be lvling)
so end in find a good spot which is not popular(world or instance) and bot for small amount of time or go full 24/7