Shipping on Shopify

I just wanted to sell a product for like $15 with free shipping everywhere, but I just realized this might not work so well.
I am new to drop shipping and I don't really know how shipping works.
Or I am just confused

If I sell a product for $15 and I just pay the price of the product + epacket shipping myself (lets say that costs $5) will I always be getting $10 profit?

or

Does epacket shipping only work for USA orders or is it the same rate everywhere?
How do I figure out the…

Shipping on Shopify