The concept of Djinn is commonly popularized in the main frame with it's relevant nature tied into Islam, though truth be known, Djinn Crafts work on the basis of 'binding' i.e through force and making the Djinn under control. Such form of practice is too vulnerable and should NOT be practiced by any common person by reading things online, either your working will fail or you may end up doing serious damage to yourself!
I've seen many peoples talk about Djinns as if they are granted slaves, there are peoples that 'sell' Djinns too, that is just scams, why? Because to have a Djinn binded with a person is a complete serious and hard practice, not at all going to work through Window Shopping.
Another thing is that peoples view Djinns to be sent by God to help us, there are stories that among such Djinns many turned up harming humans, that's why all Djinns are not good. People have thoughts that Djinns can manifest things out of thin air and many supernatural powers, which is true! But they don't know that such Djinns are of many kinds, some are truly of God himself & so will be in pure relationships, but there are many those of evil are needed to be controlled through practices are binding into objects, spell bounds etc..
Now having been said that there are pure and helping Djinns, don't get the idea of having one, at least not for purposes of selfish benefits, such pure Djinns are no different than Heavenly Angels & the others same as Demons.
Djinns can turn intimate with persons by many means, they can even get attracted by means of beauty, physique or even perfume smell, hence some Muslims believe to avoid using perfumes during evening times and go out (mostly if you are headed towards remote & isolated places, where there's lots of trees or a graveyard on way) One actually may have a personal Djinn for assistance in life by the blessings of the Almighty One.
Concerning the returns, some (Inferior) Djinns expect to get something in return for any help received by them & is a serious business, such Djinns are not of our earthly world and may just expect your own soul powers or even adult relationships.
Mostly in Islam itself, Djinn Crafts are considered to be as a sin, and according to me should be avoided & faith in almighty can have far more helpful alone with pure heart.