Origin of the funds used for the remittance.
Values:
- salary: Income from employment.
- self_employment: Income from freelance or independent work.
- business_income: Profits from a business owned by the sender.
- savings: Personal savings accumulated over time.
- investment_income: Returns from investments (dividends, stocks, etc.).
- sale_of_asset: Money obtained from selling an asset (car, property, etc.).
- loan: Funds obtained through a loan.
- gift: Money received as a gift.
- inheritance: Funds received from inheritance.
- other: Other source of funds not listed.