This is an early stage idea and I haven't got all of the details ironed out yet but;
1) The only way I see this working is me being the sole owner of the property and some sort of contract between me and the 90 other people ensuring that I pay them
2) Insurance/Liability this would be covered by the rental agents (the £600 figure is after their cut)
3) I have no real-estate experience
4) R.E unforeseen expenses, that's a very good point and not one I've thought of.
5) The income is really split 100 ways, I will get no more than everyone else involved, other than the contracted right to buy them out for property value/100 at any time
6) I wouldn't let anyone own 51%
Like I say, this really is just an idea and possibly not one that will work, but thanks for all of your feedback so far!