ANY bike is Cheap to maintain...Kinda.
It just depends ifu goto an 'Up-Himself' mechanic, that charges like a wounded bull, or goto a decently priced guy (HARD to find!!).
Or YOU can do 'most' of the basic maintenance yourself.
Trust me its not that hard, once you get a workshop manual (HIGLY recommend).
The manuals like 'Haynes' or 'Gregory's' are VERY explanitory and have great Pics to-boot.
I am refering to 'Basic' maintenance, things like Brakes, Servicing, Tuning (Spec. tools needed), General Safety checks, Parts replacement, etc.
Ok, so ive been playing with motors since i was 12, but YT nowadays has just about EVERYTHING you need to see it done, before you do it.
Recently, i had to re-build a set of Carbs for a Suzi 250 Across, searched on YT, NOTHING!!
So while i did the re-build, i filmed it. So now their is one on YT for others to see for research/practice.
Plug Plug -
So, depending what Pocket-Rocket your gunna get, i reckon do some research first on service intervals, consumable parts costs, etc. And maybe even do a 'Light Engine' course at your local Tafe/Trade school.
(light engine apprenticeship, is pretty much a M/bike mechanic qualification here in Aus., and on par with a Lawnmower mech.)
Good-luck, i'd love to know your findings and/or what your getting.
Cheers
> : )