I found that going to the ARC with my site plan, and a red lined sketch of what the addition was going to be was great.
They helped answer my questions.
Then I hired
Blue Water drafting to draw up the plans.
I want to add here that too many home owners make a major mistake of meeting several contractors and obtain bids after discussing want they want with each contractor.
you are NOT comparing apples to apples, in fact you're putting the cart before the horse.
THe better way is go and have a set of plans drawn up, cost $400-$1,000.
now go to ARC your self, if the contractor does the plans & app to ARC he has to add profit, and really doesn't want to do it.
Now take an approved set of plans and get 3-5 bids. 
you can't do that if the contractor does that!!!!!
I'm fortunate that I don't hire contractors and deal with all the BS.
I do everything myself, but not everyone can.
So shop smart!
.