It depends on the Demons. Most Demons will ask for energy in return, it makes them more powerful. If you have a close bond then maybe he ask something else or nothing. If you don't then maybe not energy, but there sure will be a price. Usually it's energy though...
Technically you reproduce energy every single day, but it may mean something else.
Depends on the demon. There are some in Tibetan black magic where you use hazardous and toxic materials to call them up along with horrid ingredients which are best not to be mentioned here. Otherwise, I'll be gagged for describing them in such great detail. Anyway, certain lamas also use their own flesh as sacrifice to demons and gods. Other lamas often perform Tantric rites of human sacrifice, which is not humane in Buddhism. Of course, there are Tsok offerings made of meat that are to be offered to the enlightened Heruka. I wouldn't recommend trying to find these ingredients or trying them out to call demons. In India, the closest I know are the Aghoris who are the hermits of Lord Shiva. However, they can be a bit different from us in ideas like using certain materials, plants, and human flesh so I won't go that far. Demons vary as each one has a favor. They are like humans, they have their own tastes and opinions. Of course, you should always have an enlightened dharmapala or a protector to be with you before doing such an invocation. Even though I only do white magic nowadays, I still am aware of the Tantric black magic. Though I wouldn't recommend contacting demons unless you've had experience in black magic or are cautious about what can happen. It's best to cleanse and protect yourself in order to be prepared on what might happen, and maybe get someone who has had experience in this. Hope this helps.
If you want to summon a demon I suggest a special ritual. If you have never met the demon you should do the following
Pour a small amount of blood in a silver bowl
Light some insence
Paint a pentagram with what's in the bowl
Say a demon preyer
That is what I would suggest
If you have met the demon you should have a way of communicating