I am a biology student so I would try to explain this in a biological view.
From a view of ecology, the vulture's ecological niche is scavenger, and a scavenger consumes the dead. The scavenger, therefore, plays a role in recycling and decomposition of the dead in the enviornment.
Vultures eat the dead, but they may attack the weakened ones near death, but not all the times. In African savannas for example, the vultures scan the ground from the sky to spot any dying animals, and when they spotted any, they land near the dying animals to wait them to die. It doesn't gaurantee a meal for them, however, since ground beasts such as hyenas have learned to look for vultures in the sky to pinpoint the weak prey on the ground, and they can follow the vultures to the locations of the weak prey and snatch the prey for themselves.
Therefore, in a way, vultures is a precursor to death to the weakened prey----the dead feed them, afterall. Is it a bad omen that they land both outside your house and your mom's office building? Well, maybe there are dead or/and near-dead tissues in both locations, so they appear on both locations. You can investigate if you want to set your heart and mind to peace. Good luck.