Some sellers will ask for a modest refundable deposit. Don't be turned off. It means you will get a better testing opportunity than you would be getting from non-qualifying demo offers. Once on board, don't be a passive passenger. See if you can manage it all, all by yourself, without hassles, without helping hands, and in comfort.
Promises are only as good as the history of the builder.
How long in business may be one guide. The point is, a guarantee is only as good as the people in back of it. A million year guarantee may not be as valuable as a one year term from someone who means it. It becomes clearer when you find that what you paid does not necessarily get you sailing as you envisioned. That you still have to shell out thousands more to make your investment work.