My advice... Don't do-it-all-yourself. Novice and pro alike can benefit from each other in DIY. You might have the shed location leveled by a landscaper; get a referral to outsource the shed's foundation to a building subcontractor; you can even have the roof's trusses made by a local truss company and the shingles installed by a handyman or roofer.
Our 14 by 24 one car garage was delivered and set up early November. The truck pulled up shortly before 7 am and left by 5 pm after the garage was completed and cleaned inside and out. Two carpenters worked tiredlessly without even a lunchbreak to make sure that everything was complete by the evening. Despite the workpressure the always had a kind word and did not mind to answer our stupid questions. We haven't seen such a work ethics for quite some time. On top of it, the garage looks terrific and matches the style of the house. When asked I will recommend Sheds Unlimited without any reservation - a job very well done!