From what i have seen and read, most shop bought coops are:
1. too small to accommodate the number of chickens claimed
2. made from poor quality materials
3. very expensive (relative to the above two points).
Like you, I am no DIY person. It may be worth checking out prefab garden sheds (preferably wood) and even looking for second-hand ones. I use an existing garden shed and it works fine for me. If you get a shed (or whatever you choose) cheaply, then you could possibly consider putting more money into the run area. If you choose a shed, it will give you space to increase your flock (inevitable), store their food and other sundry items, let you walk in - makes cleaning easier etc.
I'd suggest looking at the coop section maybe that might give you some idea of what other people have done.
Remember, the structure doesn't have to be pretty - just has to be comfortable for your chickens! Whatever you choose, please read up on ventilation.