This is old, but I'm an experienced knitter, so advice I can give!
1. For me, it was like a 2, however, I learned the absolute basics from a friend, like casting on and how to make a knit stitch. The rest I learned from watching videos online and reading in books/online.
2. Seriously, the internet is a fantastic tool for learning how to do things - there are videos and step-by-step directions everywhere. I am a visual learner, so videos and pictures make things so much easier for me than descriptions, but once you get the hang of what abbreviations mean, it gets easier.
3. It depends on how much you
want to spend. Honestly, if you're a beginner, getting stuff cheap at places like Michael's, JoAnn Fabrics, and Hobby Lobby is easy because of sales and they tend to stock mostly affordable products. However, if you start to really get into knitting, it can become quite expensive, but that's because the materials aren't mass produced. You can buy perfectly nice yarn and pretty decent needles at craft stores. I also recommend the website
KnitPicks, because I LOVE their needles (I some wooden and metal ones) and they do have some yarns that are more cost effective than some craft stores.
4. I wouldn't say knitting is "fun", I'd say it's simultaneously relaxing and challenging. It's fun when you get a few people together and knit while chatting, but usually when I knit, it's while I'm watching a movie or something at home. I really enjoy it, though, don't get me wrong. I'm kind of obsessed.
5. I would say you know you're good at knitting if you actually enjoy it and can master one technique and still want to learn more. Say you master the knit stitch and make a garter stitch scarf, then it's time to master the purl stitch and learn things like stockinette stitch, moss stitch, and ribbing. Ok, you've mastered scarves, how about trying a hat in the round? (These terms may not all make sense, but they're really easy to look up.) Basically if you keep challenging yourself to master a technique and then progress forwards, you're good.
6. Define "really get into knitting"... It depends on what you want to be able to make. If you're happy with simple things like scarves, hats, and fingerless gloves and the like, then I'd say not much. If you want to get into things like socks and sweaters that actually focus more on having the perfect fit, then I'd say a lot, because you need to not only know about how to knit, but also how to knit to specific measurements. I've been knitting for over 10 years and I'm still working out the kinks on that. (But that's because math is not my greatest strength. Also I haven't been a consistent size, which makes things more challenging for me personally.)
7. For me, it's a 9-10.
Ravelry, a social network for knitters/crocheters/spinners/weavers/etc., definitely made things more addictive because there are patterns everywhere and tons of people to talk to about knitting. I strongly encourage you to check it out!
Also another good resource is
Knitty, because not only do they offer all sorts of free patterns, there's also a lot of descriptions on how to do things.