I will try and answer your questions.
1. If you mean premade characters, than yes. I used to only buy characters, but once the Headshot plug-in came out, I haven't bought one since.
2. Is kind of a vague question, and depending on your graphics, video skills, you can purchase content and / or make it and get up to speed quickly. How good it is will vary. If you have more money, than purchase content, else make it if you have the time and ability.
My first video took me about a month, and after people told me I didn't have any motions in the dialogue, so I learned something.
3. Can't help you with anything Mac, unless it is a good recipe for with cheese I have one.
4. As for average time, that is like asking how long does it take to run a mile?
This video took 6 weeks for 19 minutes, and I had some of the animation already I mixed in.
My current project I have been (not) working on (much) for six weeks, and it is 30 seconds for the Lip Sync contest.
Animating 6 or 8 people in 30 seconds is harder than it sounds.
The First Time I Bought Condoms
I bought this scene and modified it, I need to finish this project it's funny I think.
75% of original size (was 670x19) - Click to enlarge
In summary it comes down to how much time and effort you put into it.
Creator of the free website:
PixelDatabase.Net
A Free Online Text Based Image Editor
75% of original size (was 670x19) - Click to enlarge