Series I bonds have two components: a fixed base rate and a semiannual inflation rate.
Series I bonds are inflation adjusted, which means they will have the same purchasing power in the future as they do today.
You will not be able to touch the bonds for one year after you purchase them then a forfieture of the 3 months most recent interest before 5 years.
I would also suggest that you purchase your bonds through
TreasuryDirect instead of a payroll deduction because you will have more control.