Italy Mafia Community

Do I have to be invited or apply some how?

You can apply here: viewforum.php?f=32 & follow the formats.

Both. You have to be at least level 3 to join a faction. You can either get recruited IG or you can apply in the Job Center section in the forums.
Have fun!!!!

How do I join an illegal faction like Corleone?

you will have to fill in the format that's stated right here, then post it as a reply in that topic and they will review your apply and if they accept it they will contact you IG

viewtopic.php?f=32&t=2406

Or, be a little more realistic and get in contact with their lower ranks and start working your way in. There are always ways to join factions on. Some prefer applications on the forum, others, like Corleone, refers in-game contact.