Pet Trades can have up to 5 pets on them and you can offer up to 5 pets on other player's trades. You can only trade pets for other pets and all trades are final. If you only want to send a pet to another player, you should use the Pet Exchange. Buy and sell standard pets at the Pet Auctions and
use Pet Lending to safely borrow pets. MP fees charged to move pets are the everywhere. Use the Trades Forum.