I make around 3-5k a day doing minimal stuff (farming with 1 char, selling everything on AH) - so you should be good.
See, this scenario personally makes me a bit nervous. For right or wrong, I normally tend to farm for 8-12 hours one day, and then slowly sell that stuff off on the AH. Perhaps I should change up my method, because Ski if this is working for you, and you haven't caught a ban, then it might be a good way to go. How long do you spend farming per day, and generally what do you farm? Not looking for trade secrets or anything, mind you, just generic info. I have my farmer doing cobalt ore, since it seems to be around 50g a stack on my server. I'm hoping to get around 100k in my bot's guild bank before Cataclysm comes out, and even at a low 3k per day, I could easily hit that goal. Hell, I'm at around 65k now, but I *have* to get a mechano chopper, so that'll set me back. 3k a day over the next few weeks and I'll be set.
Anyway, to answer the OP's original question, you could *very* easily hit 50k with one account within a month. What I recommend is to first look at the AH for prices on herbs and ore, to determine which way to best fill the market's need. If you see that say Mithril or Thorium is high, set out to farm that. Just remember to review the AH often to ensure that you aren't over-saturating the market, and bringing prices down. Maybe put up say 5 stacks, with a 1% undercut and monitor how long it takes to sell. If they get bought up quickly, re-list 5 more stacks. You may also want to corner the market, by buying all of that particular resource, and re-listing it and yours for higher prices. This takes more effort, since you have to continually look for people undercutting you, and buy their stuff, and relist it. Some bigger fish could decide just to list a shit ton of that resource undercutting you, so be aware of ALL the risks before you choose a course of action. Lastly, don't flood the market, because you don't want to catch a ban for your efforts.
