You can do what I did to soundproof my studio....NOTHING! With a little creativity like with my guitar fort. http://www.recordingreview.com/articles/articles/151/1/My-Electric-Guitar-Recording-Secret-Weapon/Electric-Guitar-Isolation-My-Guitar-Fort.html you can avoid the whole mess of soundproofing at home. Maybe I just have the best neighbors in the world, but I haven't had the cops called on my in nearly 4 years.

Conclusion

Soundproofing is very doable, but it's very expensive. If you are are just getting into recording, I would find a way to avoid it. Soundproofing should be done when you build your first official facility and are spending hundreds of thousands of dollars to get a place where you can create pro recordings. If you aren't ready for that now, do not bother!