I've been in and out since I was 14, most recently for a bunch of firearm charges in a high security (10 counts, surved concurrently thank god, fucking gun registry)
Rent: You work in your jail/prision, meanial jobs for long periods of time, you cant get the money when your in there, so you just get it sent to your landlord to hold your place
Telling your employer is a no no, you'll get black listed, quit.
You can usually only call people who are non felons and on a pre approved contact list, max usually 5 people, choose wisely
Get strong, stick with your own kind, and make sure you got some muscle and tattoos......
Best advice I can offer is if you get fucked with, don't be a bitch, go beserk. When I was 14 and a newbie a big skigen (native) tried to beat me down hard, he was hella fat......long story short i stabbed him with a pencil and bit a chunk out of him (He had 100lbs on me) when you get the reputation for being nuts, people dont fuck with you, and they take a shine to you, because its good for them to be your friend, and vice versa.
ALSO
Swallow as much shit as you fucking can.
Like the guy above me said, dont fuck with another persons shit, be it cloathing, jewelery or even a pencil, when you get labeled a theif inside, no one trusts you.
Oh, and if your sick, dont go to the infirmary, 9/10 times your going to get ALOT sicker
Edit: My Police appointed homes, New brunswick youth correction center in miramichi, St John Regional Jail and Spring Hill Penn
All drugs exist in jail, needles do too, watch you dont get stabbed (Happened to me a couple times, Hep C cause of it)