Tricky without knowing the weight of the unit AND the dimensions. The 9000lb referred to is likely to be the max weight the trailer can run at - which is just over 4 tonnes. That doesn't mean of course that the house is going to weigh that much - but really I'd have expected the manufacturer to give some more details on that sort of thing. Why not drop them a line and ask?
Andy
As far as I know, you must be permitted (on your licence) to tow the maximum "labelled" weight of the trailer even if the trailer doesn't actually weigh that much on the day.So it doesn't matter what the house weighs in that case.