rc is the most profitable you can actually do something with rc when you lvl you can make more money... Woodcut isn't good because im at 99 wc and i still cut yews and mages the same as i did at 80 wc
A long time. Id say a month or two of straight rc if not more.
But it is the most profitable. Im myself am working to finish heroes so I can use abyss to rc.