Yes. You just have to add yourself as a friend, and then you can send stuff over to that account. You can only send one thing a week though.
You have to get 'passes' to buy items from the black market. You can either buy these with real money, or use equus from your reserve. Different items cost different numbers of passes.
Yes, you can have several accounts. You should use only one account at a time, and the accounts should not interact with one another; for example, you may not transfer items from one account to another.
I think you mean black market items.
No. There is no possible way to remove a BM item on a howrse. You can get rid of the wings from Medusa's Blood by using a Golden Apple, but that is probably the only thing that changes...
There are several different ways to getting black market items on howrse. The most common way is to buy the items with passes, which can be bought (with real money), earned (through different ways, for example: every 5 karma points), being given a pass/black market item from another player, and/or winning passes. You can also obtain black market items by trading one or two black market items from your inventory for another item with another player who accepts your offer. Sometimes, Howrse staff are kind enough to give away free black market items to players whom complete certain objectives. (Like the September Calender 2011) - Ecclipze on Howrse
It depends on the games you got it in and the game you transfer it to, but most items will work in most games.
You can only sell black market items to other players.
he gives you black market items
You have to trade one of your bm items for it. Go to Breeding>Store>Trade Items
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All items in income statements are temporary accounts because at the year end all close to income summary account and transfer to balance sheet in shape of profit or loss to be income statement starts with zero from next year.
There are no cheats for howrse. You can only get promo codes that let you get certain items, also you can get cards. But neither of them are out right now.