Well as the title says, Dropship Spawn Method i simply just do not know how to do it.
What i'm trying to do:
Players have a Protoss Shuttle, When Unit Drops Out It Takes Away Cash Then Spawns a Unit at the Spawn Zone
Can someone lend me a hand?

When you think about it its very logical:

Always Center a location 'drop' on the dropship that covers ground only.

Detection Trigger:
Conditions:
Current Player brings a least 1 Marine to 'drop'
Current Player has gathered at least 100 Minerals
Actions:
Execute ai script 'Enter closest dropship' at 'drop'
Create 1 Jim Raynor for Current Player at 'spawn'
Subtract 100 Minerals for Current Player
Preserve

Make a similar trigger when he has not enough minerals which doesn't subtract minerals and doesnt spawn a jim raynor.

This works best with hypertriggers.
To make it more reliable always order the dropship to 'drop' (no need to recenter 'drop' in this case) and surround the drop zone with unwalkable terrain.

Thank you so much
Much Appretiated

It also helps for the trigger only to execute if a switch/death counter is cleared, and set it after executing the ai script (because the trigger can sometimes fire multiple times from my experience). Then have a separate trigger that clears the switch if the player brings 0 units to the drop location.