Some information on shared ownership
Links to some more Reading. Some pieces are quite old
The history of narrow boat shared ownership can be read here
A share of your own (2010 Waterways World following the collapse of Challenger and OwnerShips)
Share and Share Alike from 2007 (somewhat dated especially as the writer took a share with OwnerShips but worth a read to get a flavour of what to look for and ask. Part ONE and Part TWO are here.
A boat on the Midi concerns shared ownership in France. Part ONE and Part TWO are here.
A list of compaines managing boats can be found here