They're set up as shares in a company - so to sell your stake you 'simply' sell your share to someone else. A bit like how you'd sell your share of a listed company, but without the scrutiny - a bit like a timeshare, or selling your park-home. I could imagine the shares will be very liquid up to the point in time that the value of the underlying asset starts to drop, at which point they will become illiquid and more or less worthless. I can also imagine that there will be additional costs (beyond the 12.5% + vat (ie 15%) management fee) invented at some point... At the five year point there will be a formal opportunity to exit at market rates, but only if someone wants to buy at those market rates (ie, completely useless as it is the same as putting up your share at any other point at 'market rates') - if no-one wants to buy then they simply sell the property (it is not clear what happens if there is a majority that want to stay invested but the small minority can't sell their stake at the 5 year point). Of course, if they can't sell the shares at market rates then it might simply be because there is little interest in such investments, which might be because at that point in the market there is no interest in letted property investments - so perhaps the simple sale of the underlying asset might take a considerable time. And it goes on.
This is a nice simple investment so long as everything is fine and dandy. At the point in time where things are not fine and dandy this becomes a crazy investment.
I wonder what will happen?
Anyway, the investment reappraisal point is 5 years from now - so I imagine that by 5 years time there will be lawsuits.