Although ballroom isn't easy, it isn't really that hard to start. The nice thing is that you can go at your own pace.
Heres the trick to being successful in ballroom, try not to be too disappointed

PRACTICE. Practice is what divides the pro's from the con's (er... not pro's)
No matter how small your house or whatever it always helps to go and go over the steps (even if it's just in your head), and if you can't remember them then try, right after class to write all of what you learned down. If you learned a routine then write it down best you can bv. This is pretty boring to do BUT it helps a ton.
ALWAYS go to class prepared and you will always have fun.
Also try to always do exactly what the teacher says without question, some things about ballroom can seem pretty aquard (like doing lifts, being close to the other person, shakin' your hips, etc...) at first but the are normal for ballroom. Just try to have an open mind and don't hesitate, just do it.
And above all just enjoy yourself, ask people to dance if they don't ask you, Preticipate etc...