Well, they cannot "appreciate" in the standard sense, i.e. become worth more year by year than an appraisal. Why? Many reasons, not least of which: they're fine for single folks, but couples won't last long in such cramped quarters.
Lots with undervalued homes, i.e. tiny homes, on them are a poor usage of the property. Everyone, sorry to say, just can't have there own place or Oregon would have no farm land or public land left. 
Strange as it may seem, New York city is the greenest place in the USA. Tiny home people are the LEAST green folks. Period.
It's too late in history to think about "40-acres and a mule." 7 billion on the planet, pollution looming as an extinction event. You tiny homes folks are part of the problem, not the solution.