Sounds like exactly the questions I considered posting when I was planning my current trip. Now that I'm on the road (one year and counting) here is what I suggest:
Don't worry, just leave. The only hard part about long-term travel is the decision to do it. Not the money or the borders or deciding where to go or anything else. Just the decision to do it. After that, everything is easy.
But if you want the long version, as I'm certain you do at this stage, read on:
A house or a good paying job helps a lot, but doesn't really matter. I've met people on the road who left with $1000 in their pocket and traveled for years. The difference? They volunteer a lot and work regularly. Bartending and teaching English seem the best route, but odd jobs work too. Talking to these people who "just left" with little or no money, I'm not at all certain my route of saving for years is any better.
If you do save, I am convinced that income is irrelevant. The important part is saving every last penny. This begins with being debt-free and continues with sacrifice. Would you rather see a movie or travel another day? Would you rather have a one week vacation or travel another month or three? Would you rather have a

or another meal for your trip? Would you rather have the dignity of living alone or live with your parents for free rent?
By the end I was counting every last penny of expenses and justifying each against my desire to travel.
Route planning. I tried this and have long since given up the task as (a) hopeless and (b) a great way to ruin an otherwise fantastic trip. Hopeless because the world is just too big a place, even if you can find accurate maps. A great way to ruin the trip because the best part is the unexpected places you find either by accident or by recommendations from others.
I spend a lot of time talking to other travelers (All types! Motorcycle, backpack, bicycle, RV, locals running tour companies, etc.) and getting suggestions of good places to go in the direction I'm headed. This started before I even left by reading blogs of other travelers. On occasion I get suggestions from guide books (Lonely Planet), but only as an absolute last resort. From there, I wander around each country finding those places which sound interesting. Sometimes I have a map, either paper or GPS, other times I do not so I stop to ask for directions. Even with a map I ask directions frequently because most maps in places I've been in South America are completely useless (yes, including GPS maps).
I sometimes even just wander randomly down roads if the locals say the area is safe. I've found some amazing places that way.
A better route for your planning is to prepare yourself and the bike. The more you are prepared for any condition and any challenge, the more you will be free to wander wherever seems interesting.
Hope to see you on the road some day!