Hello,

Level investment is a Permanent 1-time investment. You do have to be with a medal to be able to buy it. This can be a trial Chunin medal or a longer-term Jonin medal you purchased.

Once you buy the Level investment you will get an instant return of 888 cps in return and for every level tier milestone you hit you will be able to claim the corresponding amount of cps from level investment. If you are at a level higher than the last tier, you can claim every tier directly after you buy Level Investment.