Have you created many insect farms?

I haven't got any insects or reptiles of my own yet until I find my own place, but for future reference, I'm curious about how many of you have created your own farms. I'm also wondering what level of expertise it would require, how much room your farms have taken up, various other titbits.

Obviously, the usual reason for building a farm in the west is to use the insects as feeder food which would be my intention if I got a lizard or a praying mantis, but I do of course hear of kids getting ant farms because they are fascinating.

What are the pros and cons of farms for food over buying insects from retailers? Also, if I got my first mantis, at what point (if at all) should I consider a farm, and what kind of farm would you recommend?

As an additional question, I mentioned western culture above. But in eastern culture, insect farming for food for humans is common. What do you think of that?