Why is it 根気のいる仕事 and not ある ? (example sentence)

[Enjinks]

Hello everyone,

If I remember correctly, the difference between ある and いる is about whether the noun it defines is a human/animal or not.
In lesson 12, one of the example for the world 根気 (patience) is これは根気のいる仕事だよな。/ This job requires patience, huh?

Are there exceptions to the ある / いる as I know it ? Is it a personification figure of speech ?

Thank you

[Belthazar]

Different verb - this is not 居る, to exist, but 要る, to need.

Tragically, both are usually written in kana, so it can be hard to tell them apart. The trick is that they conjugate differently - “to exist” is an 一段 verb, while “to need” is a 五段.

[Enjinks]

Thank you for your super fast and clear answer!