Day to Day Life
Ok, first things first, EVERYONE starts in Midgar, and works their way up, and has to spend a month inside the Slums, before they can take the train up, this is for 2 reasons
a) So I can see who's active and going to continue with the sim
b) To build up exp and gil, as well as general knowledge of the sim.
But after that month you can go up and down Midgar as you please.
Now, if you wish to join Shinra once on the Upper plate (advised highly unless you have the gill to leave the city straight away), you may. If you are the first to claim a job you may have it, but jobs such as General and Head's of Department cannot be chosen, I choose them. Once in Shinra you must do at least 1 mission before you can buy from it's stores, and you must stay in Shinra for at least 3 months before you can leave, this is to stop people joining and then quitting to get the good stuff. If your in the army to start with (as most will be) you start at Shinra Army 8th class, and each mission you do jumps you 2 classes. Pay is always the same until you reach Soldier.
From here you can enter Soldier by passing a mental test (which is questions on FF7 in General) and a physical test (against various opponents). If you score high enough you can then join 3rd class. Then you must complete 1 Soldier mission given to you by the General only. Then you may try for Soldier 2nd class then next month. This is the same as 3rd class but harder and better pay. Then you need to complete 2 soldier missions before moving to 1st class next month.
This is extremely hard and will take great knowledge of all things, as well as great physical strength, if this is completed you will be graced with permanent Mako infusion and will be moved to Junon Harbor.
But all this is not nessicary if you have money, if you have enough money to get ALL the way to your destination then you may leave Midgar, by buying a vehicle, this is the only way out, except helicopter or special shinra transports for the army if on missions.
I'll add to this as more cities emerge.