How to buy a hero?

How to buy a hero?

I know how to buy a hero but not how to remove the hero i allready got so i dont get 2 heros. so plzz help

FOB(For Observation) i got a reviving system and its a multi player map!

removing hero

so what i understand you want to buy 1 hero and if u try to buy a 2nd u want the 2nd hero to go away. somthing like. event player buys hero (somthin like that)
condition hero ? 1
action spawn a hero.

or

event player gets a hero
condition
action remove "hero" from game
spawn hero 2