Yes, PTAC systems are big and powerful units that can heat/cool a single living space. They need to be installed on an exterior wall so as to provide an outlet for discharge. For residential use, air conditioners are usually preffered to be more interior decor friendly and are needed to be installed on a non exterior wall. Hence PTAC units are more suitable for commercial use. I would listen to your friend, eventhough PTACs are pretty good systems, there are other systems such as split ac and central air conditioners that would fit better for residential use.