I started ballroom 4wks ago (salsa) I would like to know how long does it take to be great on the dance floor ? I know it takes lots of practice, but my hubby is not involve... I tell him I'm going to rent someone to go out and dance with me....

Pretty tough to answer, especially because "great" means different things to different people. I've been dancing since I was a kid, so that would have me going on 50 years or so. But I am not "great" by any stretch of the imagination because I never went professional with it. I teach many couples, but only as a hobby. I know hundreds of steps and variations, and I have danced in shows in front of hundreds of people, but I am not great. Oddly enough, my wife does not share my interest in this dancing hobby, though she is quite good when we dance. She's not inclined to practice much, which I do often. Don't think you have to be "great" to enjoy dancing. Just keep learning and practicing... you'll at least know when you FEEL great, which is a terrific reward in and of itself. Read and study about it as much as you do your actual work on a floor, and you'll find it quite enjoyable.