That not possible sweety, it only happens in movies.
In real life you just 'ask' some demon/spirit to help you, most demons can feel our pain and they are friendly, they might help and 'might' ask for something very little like a cup of cinnamon or a cup of honey or just ask you to talk with them.
You never really sell your soul.
And well, I tell you, take help of anyone you want but make sure you have worked yourself on it...
Go through joysofsatan site
See which all demons can help with love or money matters
If you want sit in meditation and focus on their sigil
Ask them to help you.
Simple! If they want they will connect and help you...