I have a blind friend who really wanted to saw logs...and it was simply too dangerous to be around my mill I owned at the time, a Meadows #1 with a 56 inch blade and power receder and turner.
So, I looked around and found the company in Arkansas, Mr. Sawmill,
http://www.mistersawmill.com/ and they converted a small "hobby mill", I would call it, to 5hp electric. Will do an 18 inch diameter by 8 foot long log, and with a simple extension, length would be as long as you could handle.
That is what I would call a true "hobby mill", but like small machine tools and such, they can do the same stuff....just takes longer and of course, you are limited.
Hobby milling to me would be any mill that isn't a production mill....because if you are not making a living doing this, then it is a hobby.