I dont want to be advocate for someone but just FYI, there is another difference in Islamic and non-Islamic mortgage. If for some reason, you can not pay your mortgage, you dont lose your house, instead its sold and you get your share while in regular mortgage bank gets its money back by auctioning the house and you get kicked out…
if someone want to get into it, there really is no gray area as far as interest is concerned, lying, wasting food, money etc are concerned and all these are common practice in muslims (including myself)