If one wish to practice vajrayana, he must have the core of
mahayana which is bodhicitta, if not, he will not succeed.
As mentioned, vajrayana is part of the mahayana buddhism, just that
the practice is different, it has a lot of convenient method that
enable the practitioner to become enlightened very quickly.
But if the person's motivation is for himself only, don't even have
the worldy renunciation and breaking the vajrayana precepts, he
will go to the lower realm very quickly also.