Here are some things I've noticed in researching building my own coop vs. getting ship-to-build-at-home types.
If you are handy, even a little bit, building your own would be the way to go. It will last longer and be stronger. There are so many cool plans online as well!
With that being said I purchased a build at home kit online with the intention of beefing it up to keep it secure for a couple years hopefully.
The wood on these kits tend to be really light, latches and sometimes hinges are not the best quality. For mine, I will be replacing a lot of the latches, painting and waterproofing the exterior, putting hardware cloth on the bottome of the run. All told will cost about $400.
In a couple of years I plan on building my own, but I want to really take my time and plan it out properly. I have 2-day old chicks in a brooder right now, so no time for lengthy planning
Good luck with your decision!
Iri