"I am at hire" vs "I am for hire"

[Rosa Rimli]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #664 "Prepositional Phrases - At, By, For and To (2)", question 9

If you know anyone who needs anything built, I am ......... hire. I can build houses, sheds, decks etc.

(a) at
(b) by
(c) for
(d) to

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #664 "Prepositional Phrases - At, By, For and To (2)", answer 9

If you know anyone who needs anything built, I am for hire. I can build houses, sheds, decks etc.

Correct answer: (c) for

Your answer was: incorrect
If you know anyone who needs anything built, I am at hire. I can build houses, sheds, decks etc.
_________________________

Why i am for hire is not correct,
how i am at hire is correct?

Rosa Rimli

[Mister Micawber]

'For' is correct, 'at' is not. The correct answer is indicated above your question.
_________________
Native English teacher at Mister Micawber's