Start a sentence with "of"?

I would like to know if we can construct a sentence beginning with "of".
I have surfed the Internet and some suggest that it is grammatically correct to start a sentence with "of" as they treat 'of' as a 'conjunction'.

eg1: "Of the top ten languages in the world, the least widely spoken is French"
eg2: Because I have no money, I have to work.

In the above examples, undoubtedly, 'because' is a sub-ordinate conjunction. However, I was taught that 'of' is a preposition in lieu of a conjunction, so... can we really use "of" in this way to start a sentence?