The prefab coops are fine for individuals that are not sure if chicken keeping is the thing for them. They spend $200+ and do get housing that is fine for short term. They usually upgrade to something better , once they know,,,,,, chickens are there to stay.
The easiest way for a descent coop, is a garden shed conversion. Wood, metal or plastic all can be converted into good coops. I would prefer wood as first choice, with plastic close behind. Metal would be third choice, since slightly harder to modify for chicken use. (but not impossible) All depends on your working skill level, and type of tools you have available.
You would need to provide much ventilation, especially during summer hot weather. That would be cross ventilation. For year-round ventilation, you also need plenty of ventilation up high at roof line/ridge. That is to vent humidity, and ammonia.
Not sure of your budget situation, but you may consider getting a used shed from Craig's List posting. They do go for little ca$h, if somewhat dated. I have seen them for free, just to remove. If you are handy, then one of those would be a cost-effective route to try.
WISHING YOU BEST,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,and