For a city to pay for larger capital project, cities sell bonds to pay for the projects. Bonds are sold to investors who looking for a stable return in the future on the money they invest today. The city commits to repay the bondholders with interest over a specific time period (often twenty years). Because the repayment is several years, the city only uses bonds for projects that will have a life span of multiple years, like roads, parks and buildings. The city strives to typically put bond programs forth to the voters every 5-7 years.