At the moment there's no server locks in place outside of high-population servers which you can get around by waiting until early morning hours in the region of the server you want to transfer to (if the destination server happens to be highly populated). One person above did mention the gil limit though, which is something like 1m on the character and around 100k per retainer, so definitely watch out for that and if you absolutely have to transfer that character, make sure to really do your research in regards to the economy of the destination server beforehand.