Greetings. Now that I'm done with SkyBlock1, I'm selling my island for 20K. If you want to buy it, reply with your IGN. It has some villagers too.
You can pay the person the amount of money, they add you, and then they leave. Then it's your island. But you can't hand off an island to someone/make them the official owner of thus island.
Guessing it would be a scam then. The player could get staff involved, but I don't know if they can do anything about it.
I believe the only way to leave an island in Skyblock if you are the owner is to delete it, thus deleting the whole island so the other added player gets nothing. If you are the owner of an island and someone else joins you, you cannot leave the island and it still be there since when an island is deleted anyone on the island gets automatically sent to spawn.