i am a hongkonger. what do u mean by pension houses?
we've got guest houses/hostels, very cheap ones like shown in this link:
http://www.hostelsclub.com/hostel-en-9117.html?aff_ID=149
there is nothing near the airport i am afraid. unless u stay on lantau island in holiday flats. it's accessible by bus from tung chung which is the connected by buses to the airport (5 mins away only).