All the quests from South/North island,Oslya and stoowa isle are for free.
I usually take their offers[The price can be negotiated]
Japan
-Kanako -around 3k-
all the other quests -offer
China
-The quest with suns - 1k
-The Immortal fox - 500g
-The crane - around 2k
all the other quests -offer
Koreea
-GS- offer
-Cherish the Animals - haven't tried it yet
-Thief in Inchon - offer
Maya
-Sasha - offer
-Olaya - offer
-Huge Crocodile's invasion - offer
Rome
-Heave Levy - offer
-Be Brave - offer
-Prove it - offer
That's it for now.