[Tower Defense] For anyone making a TD

[Noctiss_Season2]

PLEASE do not base your "selling tower" mechanism on TRAINED UNIT event
the tower will get a rally point for no reason and each right click is gonna be rally point setting instead of attack clicks which people need
if you do sell
base it on a dummy Channel spell
Unit uses spell
condition spell = dummy channel
action
Selling mechanism

 

[Macadamia]

The best way I have found, and I use in my map, is to use the selling of a unit with "goldcredit" as a model for example.

If you add it to the tower with triggers, you can even display the gold refunded on the icon itself by setting the max stock.

 

[disruptive_]

Maybe basing it on a selling item event?
The disable ability functions (BlzUnitDisableAbility) works on rally ability too and can be used if such ability becomes pointless.

 

[Macadamia]

For some reason, I had to give up on selling item events. Cannot remember exactly what went wrong, what I know is the version I made works beyond expectations and displays the total tower cost, don't think I can do much better than that at this point.

 

[Kapharna]

I dont see why the trained unit event type trigger is a problem. You can remove the rally point ability itself to counter this problem. In action - unit