noun
source of funds; funding source
Refers to where money comes from, such as an organization, person, or activity that provides financial resources.
このプロジェクトの資金源は企業からの寄付です。
The funding source for this project is donations from companies.
警察は犯罪組織の資金源を調査している。
The police are investigating the criminal organization's source of funds.
財源 is often used for public or governmental financial resources, whereas 資金源 is broader and can refer to any source of money.
Compound of 資金 (funds) and 源 (source).