Just one, but it takes him 20 episodes.
To screw in the lightbulb.
I'm sorry, but I'm afraid I cannot do that
Two. One to change it and one to yell "Ta-daa!" when he's done.
Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes.
There's 20 of them.
20 after 1.
20 Episodes and Krillin dies.