I've done several single crochet afghans and they have been very popular. Because it is a basic stitch the whole way, I've found them to be quick because I don't have to thik about what i'm doing. Go for it!
I'm sure it's okay to do this but it could be very time consuming. You may want to look online for ideas and techniques on knitting to learn more. There should be a lot of good resources available to show you what you need to do to get started.