GH is not the "holy grail" of mass-building...nor is it a pre-requisite for getting massive, as some would have you believe. Certain individuals (usually those with an agenda) would like you to think that unless your taking huge dosages of GH, your chances of ever getting to be pro size are next to impossible. In fact, GH is not going to add much size no matter how much you take.
Now, GH will add the typical 4-7 lbs (this number can vary) of muscle fullness, which is wholly water (both sub-q and I.M.), but the primary mechanism through which GH builds muscle size is through it's ability to raise IGF-1 levels via the liver. No matter how you slice it, muscle growth through IGF-1 elevation is a rather slow process and won't build nearly the same degree of potential mass as AAS can. In addition, the IGF-1 produced by the body is less potent than the LR3 and DES forms of IGF-1. On top of that, the capacity of the liver to elevate GH levels through GH use is limited.
Now, when using high doses of GH consistently, IGF-1 levels will rise sbstantially...and no doubt, this will help build muscle tissue, but do not believe for one second that this IGF-1 increase is a monster muscle builder...or that there is some magical synergy that takes place when using GH and AAS simultaneously, which will cause your muscles to "mutate".
If I sound like I am slamming GH...I am not. I think GH is a great drug, but this commonly held (false) notion that GH is absolutely essential to getting big is pure bunk. One of the reason why GH is so well-liked is because it produces a variety of effects concurently, which can signigficantly alter ones appearance. These cosmetic benefits (as far as they pertain to BB'ing) are fat-loss and an increase in fullness. So, in the first few months of a BB'r taking GH, he will notice both a visually significant increase in fullness (which makes it look as though he has grown), as well as visually noticable fat loss (most of the time). Furthermore, this reduction in BF% generally makes the individual's muscles appear even larger than they are. So, when this relatively small size increase and moderate BF loss are combined, they cause an apperance change that "looks" more impressive than the sum of its parts. Any further size increases which take place after this initial period will be slow, at best. GH will be no means add 20-30 lbs of muscle fiber to your physique, no matter how much you take or how long you take it for.
With this is mind, only you can decide if these benefits are worth the financial cost. Many think they are, but I also think many aspiring BB'rs place themselves in a position of irresponsible finacial strain because they think they "need" to take GH in order to achieve their muscle-building goals, when in reality they could continue making great muscle-buildimng progress for years without any GH at all.
GH does a lot of great things, but don't be lured into the mentality of thinking that just because you use GH, you are going to automatically be 10 steps closer to attaining pro status.