You could do woodcutting and just sell all the logs you cut from the beginning of level 1. In addition to that, you could fletch them to make some maple bows (u) to sell to alchers and what not.
Fishing is something else that is easy and low. Get to level 40 and just fish lobbies. Can make around 80k p/h I believe, possibly more just depends on level and what not. Getting to level 40 should take a couple hours if not less than that.
Other skills take awhile so it just depends on how much you need and the time span. Mining would be good as well.
Skills like RC and stuff take too long for what it sounds like you wanna do.