Don't even think about GH at 17!!! At 17 I would seriously reconsider cycles like what you are describing above!! Wait until your body has fully matured or you will POSSIBLY cause yourself problems you don't want.
As far as why people don't use it more. I believe there is a few reasons:
1) Cost
2) Fear of the sides, which appear to be dose related. This is one I believe is overblown, except of course in the case of high dosage use...
3) The lack of clear understanding as to how to use and what dosage to use GH. You will find many answers to the question "what dosage will result in real mass gains". This leads to bros improperly using it and experiencing little to no gains. Those bro's then propagate the belief that GH does not work. When in fact the dosage, diet, ancillary drugs, or other factors were not accounted for.
4) Cost again!!!! Using it improperly as I noted above is a serious waste of money!!! You can get alot of AS for the cost of a single kit of GH...
The question of how much per kit for Serono Serostim 126iu from $450 - 700 per kit. Now reallize you will need in the neighborhood of three plus kits for a good cycle... This is a very general estimate without knowing anything about the person, stats, age, ect....