TOPIC: commercial inspect

I'd like to get certified for commercial inspections.  I'm wondering where the rest of you took your class, the amount of time and approx cost.  I see NACHI has a free one online but I'm not sure if that will give me enough info.  I have no exp. so I don't even know how different commercial inspects are from HI.
Thanks

There's no state commercial certification that I know of in any state. Best way to learn is to tag along with another inspector on some jobs, take the free online classes and get into a live class too.

How different commercial is totally depends. For example a 4 unit residential building is considered a residential but the inspection is extremely close to a normal home inspection (might be larger hvac & plumbing systems).