Building that gives income

[dosehunter]

hi i've searced in this forum but couldn't find exact what i where searching
i'm making a map where the player can build a farm
and i want the farm to give income and the farm can be upgraded and I want it to give more Income
Like if Farm 1 gives 1 per 2 second and farm 2 gives 2 per 2 second can anyone please help me
THX

 

[Kala]

Making test map...
Takes 5 min

Edit: DONE

 

[dosehunter]

oohhh THX a lot man