No, for any number of reasons.
First, the existence of the soul is not proven.
Second, if it does exist, it's what makes you you. If you sold it, "you" wouldn't be anything.
Third, the existence of demons and ghosts is not proven.
Fourth, even if they did, you can't become a "half demon" or "half ghost" any more than you can become "half rock."
If the question is referring to trading in the "human soul" in exchange for becoming a demon and not suffering consequences in hell, then the Biblical answer is "no." For one thing, the idea of "selling a soul" to the devil is really a mythical one which I believe was first really explored in an old legend about a man called Faust. There is no Biblical basis for the idea that one could bargain with demons or Satan in order to secure a place in the afterlife. Satan is described as the "power of the air" or "cosmos" referring to the idea that he has some power in this world, the Earth, right now. All the descriptions of him in the afterlife, refer to him as being rather powerless, as in Revelation where he is described as being thrown into hell, where he certainly does not want to go but clearly has no choice (Revelation 20:10). You will notice that, if you ask your average person, "Who is the ruler of hell?" Something like eight or nine out of ten will say "Satan," but this is Biblically completely incorrect. The scripture makes it clear: hell is for Satan specifically because of what he's done to corrupt the earth, and God wishes that all of His children (us, the humans) would choose Him and thus avoid ending up where Satan goes (John 3:16). Satan doesn't rule hell and the demons aren't spared punishment, on the contrary, hell is for them and not us (Jude 1:6; Peter 2:4). Finally, your soul is not able to be "sold," but can be willingly given only to God. I suppose that someone could attempt to sell their soul in exchange for something, but there is no Biblical indication that a demon could truly "own" your soul. See the verse in which Jesus says "What good is it to gain the whole world but forfeit your soul?" and also "What can anyone give in exchange for their soul?" (Matthew 16:26). He clearly is demonstrating that though it's not possible, even if it were, it would not gain us anything.
No. You are human; deal with it.
I think Inuyasha should stay a half demon because if he's a full demon he might lose control of himself and kill his friends.
No he is a half dog demon one of his enemy's is a half wolf demon no Koga (enemy) is a full wolf demon
She NEVER used the Shikon Jewel to become a demon. Not in the TV show, SPOIL OF THE END: Kagome makes one wish on the jewel, that is will disappear forever, END OF THE SPOIL Its up to YOU how she might have become a half-demon.
as far as all of my3year Novice ghost research I can say that theres no such thing as a half-ghost-person...trying to kill people... that's all I can say there is no such thing like that but if theres any evidence of it message me Rayquaza80--
HALF DEMON OF COURSE! she said that she likes him the way he is so of course she marries him when he is a half demon!
Inuyasha is a half dog demon and half human. His dad was a Full dog demon while his mother was human, which makes Inuyasha a half demon.
InuYasha is half-demon because his father was a demon and his mother was a regular human.
Not around Kagome. She always knows how to get him back to his half demon. Her love for InuYasha has always proven stronger then any enemy that may try to get him into his full demon form.
hanyou is the japenese word for half demon Im japanses but i never hers of "hanyou" ...if you want to say half demon in japanses then you shouls say " Akuma no half "
Inuyasha remains a half demon.
No. At the end of the series, Kagome is shown, still human, living in the Feudal Era as a priestess. She did marry InuYasha, so its up to YOU to decide how or if she becomes a half-demon.