If an imam, muezzin, or mosque caretaker leaves their position for any reason, they cannot be given money from the mosque’s funds or donations afterward. This is because the money collected for a mosque is considered waqf (endowment property), which must only be used for mosque-related expenses.

These expenses include things such as salaries for the mosque staff currently serving and other necessary needs or maintenance of the mosque. Therefore, funds already collected for the mosque cannot be given to someone who is no longer serving in that role.

Islamic scholar Allama Nizamuddin also discussed the rules regarding the use of waqf funds. He wrote that if the mosque administrator (mutawalli) wants to transfer such funds to the imam or muezzin, it is not allowed unless the person who originally established the waqf clearly included this condition.
(Fatawa Alamgiri, Volume 2, Page 463)

However, if members of the mosque administration or people of the neighborhood wish to help a former imam, muezzin, or caretaker because of old age or respect, they may create a separate fund. They can contribute to it themselves and encourage others to help as well.

Such assistance is considered a good and rewarding act, but mosque donations or official mosque funds cannot be used for this purpose.