I've never bought plants, or sowed seed. Its so easy to propagate through Division.
I got mine from Steve, and since then I've divided it several times, giving clumps to Fiona, and also back to Steve ;-)
For me, its virtually maintenance free - it gets on growing year after year with little help from me. Despite the joke : "Do you put manure on your rhubarb? Ohh, I use custard!", I just add grow-more maybe twice a year.
This is the first year that I've tried forcing rhubarb, by covering it with a dustbin to prevent light getting to it. So far so good, the stems are much larger than the control (without the bin), but not quite ready to be harvested...
The first crop is in ready by early to mid-March.
Divide mature plants every 5 years or so to prevent overcrowding. Late Autumn to early Spring (November is recommended).