make it (your) business to (do something)

to decide you will take responsibility to do something.

He made it his business to find out what happened to the money.

• you bet your sweet ass
• You bet your sweet ass!
• you can bet on it
• you can bet your bottom dollar
• you can bet your life
• you can kiss goodbye
• you can kiss something goodbye
• You can lead a horse to water.
• You can lead a horse to water but you can't make him drink.
• You can lead a horse to water but you can't make it drink.
• you can say that again
• You can say that again!
• You can talk!
• You can't judge a book by its cover.
• You can't keep a good man down.
• You can't keep a good woman down.
• You can't make an omelette without breaking eggs.
• You can't make a silk purse out of a sow's ear.
• You can't make bricks without straw.
• you can't miss it
• You can't say fairer than that.
• You can't teach an old dog new tricks.
• You can't win 'em all.
• you could cut the atmosphere with a knife
• You could have heard a pin drop.