“No such thing as a free lunch” (alternatively, “There ain’t no such thing as a free lunch”, “There is no such thing as a free lunch” or other variants, sometimes called Crane’s law[1]) is a popular adage communicating the idea that it is impossible to get something for nothing. **The acronyms TANSTAAFL, TINSTAAFL, and TNSTAAFL are also used. **
You are right about the “under”, though. I “accidently half a word”, there. Will fix.