i agree with jaanwaars advice. and jaanwar i didnt know u can be so mature somtimes.
But obviusly whether hes indeed that or not you should expect for that he would be at tip-top mr polite, mannered man at the proposal visit. Dont get over-whelmed.
The other important thing is to truly assess his personality is find out how he treats and deals with others aswell as his and your family/relatives.
how does he behave at work/public/school
mybe u could find out whats things hes into, what public places or memberships he regularly attends:
i.e: a particular mosque, leisure centre, cafe, bar, nite-club.
you could go there and ask/check hows he behaves and whats hes like.
Its hardwork acting nice/polite. There must be some places/some instances where he bes himself. And this is what u need to see.
or maybe girl...if u have indeed gat a lot ofmoney...like jaanwaar said hire a 'private investigator'. He'll do the job for u.
But of course u got a ensure its a bonafide investigator etc