Public-private partnerships (PPP) can be employed to provide public rental housing for young graduates, which has been urgent to achieve social sustainability in China. However, few studies have been conducted to investigate the financing structure of PPPs, particularly the ratio of private investment, which is important in initiating a PPP project. This study develops a robust model to determine the financing structure through considering the uncertainties in operation. A case study in Hangzhou demonstrates the process of the model. The relevant findings provide private investors and the local government with effective references for negotiating the financing structure of a PPP project.