I'm 50, stayed home and raised kids for many years, and finally finished a BS in MIS '99. I have worked for the past 6 years in IT, and realized very quickly in to that career how much I hated it. I sit in a cube, create documentation no one really cares about once it's met its deadline, work with users who can sometimes be so demanding and obnoxious about nothing that's really life-and-death, and don't have many options with my schedule or job duties.
You are only in your 20's and worried about switching careers? Give yourself a break....if you end up not liking nursing, you have about 40 years of worklife ahead of you to return to what you're doing or try something else. I forget how many careers they say people have on average these days. Lucky you if you can figure it out sooner rather than later.
As for the financial end of things, if you have a supportive husband who's behind you on this, I wouldn't lose a minute of sleep over it. Unless you're out in the malls spending more than the two of you can make, take this wonderful opportunity you've got!!