onto a good thing

on to a good thing

In a favorable job, position, or situation that has the potential to become very advantageous, lucrative, useful, etc., in the future. A: "Because I can work from home, I can look after the kids when my wife goes to work." B: "Wow, you're really on to a good thing here! Your new boyfriend seems really sweet—I think you two are on to a good thing.
See also: good, on, thing
Farlex Dictionary of Idioms.

*onto a good thing

having found something useful, promising, or profitable. (*Typically: be ~; get ~.) This is a great scheme. I know I'm onto a good thing. I'm onto a good thing. I'm sure I am.
See also: good, thing
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

onto a good thing

mod. having found something that is to one’s advantage, such as something easy, profitable, inexpensive, etc. I think that Bill got onto a good thing when he opened his own store.
See also: good, thing
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • be on to a good thing
  • be onto a good thing
  • on to a good thing
  • to the good
  • to windward
  • to windward of
  • to windward of (something)
  • windward
  • place in the sun
  • a place in the sun