Is money earned from a job that does not require constant attendance permissible, except when there are malfunctions, and is employment through واسطة (mediation/nepotage) unlawful?

If an agreement has been reached with the hospital administration that one should only go when needed and called upon to fix a malfunction, then there is no harm in not going unless the need arises. The salary received is permissible, as the determining factor is the agreement, and the contract is the law between the contracting parties as long as it does not violate Islamic law. This is based on the Almighty’s saying: ﴿O you who have believed, fulfill [all] contracts﴾, and the Prophet's (peace be upon him) saying: “Muslims are bound by their conditions.” There is no harm in employment through intercession if the employee is qualified for the position and does not take the place of someone more deserving.