When gov requires buyback
When gov invest money as LP, the GP usually requires investees to buy back after say 5 years, with annual rate of up to 8%.
The equity investment is essentially a 5-year convertible loan that carries interest rate.
If things go well, gov should never lose money on these investments.
When gov buys you back
In rare cases, gov may promise to buy you back – e.g. Shenzhen gov promises to buyback 保障性配售住房, it applies an annual discount of 1% or more.
You will earn a negative interest rate annually.