Good Riddles

Question: When it's warm it has something warming it, but when it's cold it's naked. What is it?

Question: A man built his house above a river between two trees. He attaches his house to the middle of the two tree's trunks. He does this because the river rises by 2 inches each years, but the trees grow 1 inch each year. If his house is 4 inches above the river how long will it take for water to hit his house?

Question: An apple tree has apples on it. A storm comes through and there is no longer apples on the tree. But there isn't apples on the ground either.

How can this be so?

Question: When you bend me I'm kind
But I'm very hard to find
I'm easily sold
and rhyme with this when told

What am I?

Question: When is a door not a door?