I've read quite a few posts about people wanting to live a more affordable lifestyle aboard, but that hasn't been my experience. Decent boats (one that you would feel happy taking off the dock) are expensive, and parts and maintenance can be ridiculous in terms of time and money. Boats, especially sailboats, are complex pieces of equipment.
One can look at it as an investment, but living as a couple in an apartment would be cheaper, at least where I live. Many guys around here have old boats not worth much of anything (easy to do when you're single) but if you want a nice boat and intend to keep it that way, it will be a major investment in time and $$$. It's cheaper than the house in the burbs sure, but there are many other ways of living cheaply. I suspect the romance of the thing is often a part of why people choose the lifestyle, whether they admit it or not. I can't believe the number of folks I've met that went "Oooooo", when I told them how I live, and yet they've never done it.