good used bikes for under $3,000. not likely. you´re going to need something in at least the 1000cc range. on a cross country trip comfort is a must. so is dependablity. if you have never done this before you´ld be better off planning your adventure for at least a year, maybe two. you are also going to have to pack everything you´ll need on the road. cold weather gear is a must regardless how hot it is. so is rain gear. i´ld suggest speaking with people who have done this before and get thier thoughts. don´t just buy the first big bike you come across and go. there is a lot to planning a trip by bike. you need to take EVERYTHING into consideration. p.s. if you are really serious, and i belive you are, you need to get some road time with the bike before you go. good luck / be safe.