i am currently in the same position, sitting my Standard Grades and being chicken mad.
I also breed chickens as a hobby,
if you but specifically buy "Hatching Eggs" then the seller intends the eggs to be hatched,even if they do not specify, you can almost guarantee they are for hatching (when bought over the internet) i wouldn't worry about upsetting the breeder, once money exchanges hands they are yours to do as you please.
I wouldn't rear your own unless you have a high proportion of same breed hens, for example Light Sussex, if you are wishing to sell the birds.
I only really breed from my Light Sussex as i have kept a family strain (with out becoming inbred) going now for about 6 years, and have some show quality birds and the fact they are the only birds for which i have a matching male.
I must admit i am a little bit of a "snob" when it comes to hatching in that i only go for pedigree, or fancier breeds, this is just my preference, it is not a necessity.
I breed my birds for selling mainly and to keep a strong and healthy strain going. like Annie says, you do need to think about what you are going to do with, any extra males, and why do you really want to breed,. and another thing, don't count before they hatch, i made the mistake in that i had a list ready of people wanting hens, and all my eggs failed due to being X-rayed in the post.
Good luck
Cameron