[Doctor_Fegg]

4: People are building legal barges. You can pay £90k and buy one off the shelf[1]. The difficulty is finding somewhere to moor it: London's waterside is as much in demand as land in the city. You'll have to pay the riparian owner for this. Tidal Thames prices are very high; historically the canals have been lower, but they're largely full up.

In addition, the waterway authorities don't really want more 'liveaboards'; they place a lot of demands on waterway infrastructure yet it's difficult to charge them much (for legislative reasons, and getting legislation changed is a slow and unlikely process).

[1] http://www.newandusedboat.co.uk/new-boats-widebeam.php