Is it a condition to investigate people's needs before giving them charity?

Voluntary charity (ṣadaqah mustaḥabbah) does not require strict investigation (taḥarrī) and is permissible for the wealthy without dispute, although it is recommended for the wealthy to refrain from seeking it, and it is disliked for them to expose themselves to receive it. As for obligatory charity, like zakat (definition), strict investigation is required, and it is not valid if there is doubt about whether the recipient is among those entitled to it.