Earn (one's) keep verb phrase
Work in exchange for food and accommodation.
They will allow me to live here rent-free, if I agree to earn my keep by helping out with the cleaning and babysitting.
Be worth the expenses spent on someone or something
If you can't earn your keep, you will be fired.
This machine earns its keep as it has helped me increase my productivity.
Something would be suitable or useful in a particular situation.
To be useful.
To be particularly useful or helpful.
The verb "earn" should be conjugated according to its tense.
This idiom has been around since the 1800s. The term keep refers to room and board. People used to work for accommodation and board rather than money in the past, especially on farms. Earn has the same meaning as it always has in the expression: to obtain something in exchange for labor.