We bought a share in an ownerships boat in 1994 because it was a lot cheaper than hiring an equivalent boat. We sold the share in 2001 because we bought our own boat. Taking all the costs into account (initial outlay minus what we got back when we sold it, maintenance, mangement fees, diesil, pump-out and gas) it came to about £1100 a year. Hiring in 1994 was about £600 a week out of season and £1000 in season. So provided we took 2 weeks holiday a year on the canals it was cheaper.
Prices have changed since then but I think the comparison is still valid.
Share ownership may not be for you (it won't be for everyone) but on cost grounds it won for us.
MM