Answer:
I have no weight but I could destroy a mansion. What am I?
When you buy me I am costly, but the only use I have is hanging only. What am I?
I mean goodbye for South Americans.
I am not a toy though many use me for pleasure. I have a butt but I cannot poo.
When young I am sweet in the sun. When middle-aged I make you gay. When old I am valued more than ever.
Runs over fields and woods all day. Under the bed at night sits not alone, With long tongue hanging out, Resting at your feet until we go for a walk