This is probably hollywood only too but as it is often pictured, is it possible to summon a demon (not as an physical entity, that i obvious)
and forge a pact where he helps you or follows your commands or such and will get your soul in return once you die?
basically good old selling your soul to have demon help, is that in one way or another possible?
I can imagine that no physical demon boy will show up but I wouldnt deem it impossible to do the whole soul for lifelong subordinance pact on a ethereal plane or whatnot.
Is there generally such a thing possible in one way or another?
I never understood what the value of a soul is meant to be, that anyone would think a demon would want anything to do with it. You can forge pacts with demons, like you can any other sort of spirit that's interested. Though that's the catch, if they're interested. I'd recommend doing your homework on varieties of spirits and, since it seems to be your main focus, particularly demons. Working with a demon for the sake of working with one serves no end for you or them. Know why you want to work with them, have a specific intent in mind. If it's merely curiosity, I'd recommend that you stick to just studying them from afar, and keep in mind the first rule of conjuration: Don't raise something up if you can't put it back down.
Generally working with demons is a transactional exchange. Very business like. Although the concept of selling your soul to the Devil or the demonic is a Christian/lightworker concept that doesn't really exist in the demonic paths. What you're referring to is something of a contract/agreement with an entity, be it a well known demon/deity like Lilith, Lucifer, Belial, etc. or some of the lesser known/lesser entities that may or may not be Goetic or from some other system of demons.
The exchange typically involves some sort of offering, acknowledgment, something of value to the demon in question. Eligos for example likes Copper, the number 7, and the color yellow/gold.They have no use for your soul. They'll take it, but it's sort of like giving a US cashier Canadian coins. It kinda has no value to them at all.
Also it's entirely up to the demon whether or not the transaction is completed. If they want to work with you and see value in working with you, then you probably got yoursef a deal. With that comes consistency and dedication to whatever it is you are asking of them until said task is completed or until they decide to break the agreement. That being said, if part of the agreement is you delivering commands to a demon, it's highly likely they won't work with you. Lesser demons usually only answer to demons of higher rank or those who are in charge of their legions (see Goetia). Even then most demons (in my experience) embody the archetype of the Adversary; theyare rebellious by nature.Sounless you have some sort of position in a demoniclegion, chances are you won't get a demon to do jack for you. A familiar however is a different story.