When do I need to pay?

Hello,
I just installed the Epic Game Launcher and would like to create a map for one game, which will be, if it success, for free as a downloadable mod. The reason why I am asking is, that I am little confused about the payment policy, do I need to pay for the product which I downloaded from you, Epic Game Launcher, or after I downloaded the dev kit which I will probably need to create the map (the game is ARK Survival evolved , apologize if it looks like comercial or smth) or, after I will upload (again, if it succes :smiley: ) to steam workshop ? I’m kinda newb in this and don’t have much experience in it, so its 95% chance that it will fail but still, want to just test it if I am able to do smth like this, but how I said at begin, I am little confused about the payment.
I understand the 5% royalty from earned cash , f.e. 100usd=5usd need to pay you, but if I didn’t get any money from it, do I need to still pay something like, product cost,licence or renting fee ?

So to make sure I understand, you’re only talking about mods to ARK Survival?

Yes,I am talking only about mods to ARK Survival.

ARK mods aren’t monetized, are they?

Haven’t seen any yet, so if I am understanding it right, I can use the dev kit for “free” ? Until I will start gaining money from it, like if someone will donate or etc ? ? (But ARK mods on steam are free to download and use)

If there is no monetization of the ARK mods, then there is no royalty for you to owe. Normally the ARK developer will take care of royalties on the game ARK instead of you. But if you monetize in a way where only you get paid (seems unlikely), we can discuss again.