How do you find the basement in leaf green?

the only way's are that you start with bulbasaur,start with squirtle and see it with your rival or get it from a friend or get fire red and trade it to leaf green

Firered can catch growlithe not leafgreen trade one to leafgreen. i heared you can catch it but its rare to get it. like he said or trade it.

trade from fire red

You can get it at Vermilion city but you need a spearow because you need to trade with a girl with that

You can find hypno in berry forest on three island also train a drowzee to level 26 to evolve it to hypno.