The uni low down...
A simple uni costs about 60 to 120€ or so new... The model I got is about 200€ (it is really a muni, I'll explain) - middle high end. Learning to ride: two chairs or crutches or a wall, work on balance by looking at the horizon not your feet and practice, practice, practice, practice. Takes 5-15 hours over as many days...
If you think of starting get a 20" or 24" - good learning unis
I learned in college and am now re-learning mostly from scratch.
Some great resources out there
http://www.unicycling.org/http://www.unicyclist.com/online shop in Germany -
http://www.einradladen.net/shop/where.phpgloves, helmet and shin guards (patience, music and beer) - these are good friends!
Oh and do not use ski poles - I have seen one nasty accident.
Learning:
http://www.unicycling.net/learn/I bought mine near Paris (at a bike shop where I spend a lot of free time ... I was actually looking for a tandem

and a derailleur for my daughter) but off the net they are quite easy to get.
And finally - a muni - the m stands for mountain, as it is pretty flat around Munich and I need a challenge...
Some of my muontain bikes got stolen before my first move to Munich - I am looking to replace these bikes - but have not yet decided to go road, single speed or what (the Alps are both close and far away). This seemed like a good short term solution for a monkey.