I'm not a scholar on Buddhism, which seems to be the likely origin of tulpas, but I am quite familiar with the western occult thought-form of tulpas, which is, yes, through either serious meditation or a series of magic castings a tulpa can be created.
It can have a degree of will and independent thought, too.
That's what intrigues me so much. Similar to the Jewish Golem, they can become violent, aggressive....