Turnips - Yay or Nay?

I buy them occasionally and usually when I do buy then I have like 99 999 bells on me so I can buy a whole ton of them.
"I buy them all the time, they are my main source of money."
I don't see how anybody can have a main source of money based off of turnips. I guess they would sell extrememly high and buy furniture then deposit at the end of the week? I don't know. I just occasionally buy them.