Where does the corruption start?

Corruption starts within a person. People desire money/privileges / position etc and are tempted to accept bribes or do certain things for their own gain and so they become corrupt. Corruption exists in many places of work or government.

I think these verses from The Bible put it quite well:

Jas 1:14 But we are tempted when we are drawn away and trapped by our own evil desires.

Jas 1:15 Then our evil desires conceive and give birth to sin; and sin, when it is full-grown, gives birth to death.