Am I making a good decision or a horrible mistake?

That's a horrible mistake. Sure you don't have a problem with her sleeping with guys right now, having parties right now, stealing right now, working 3 jobs right now, and drinking right now but living together is a whole other thing. And her paying the majority of the bills can go bad VERY EASILY too. There's a reason why alot of people can't live together even though they get along great and if you move in, you're going to find out the hard way.