Just remember that not all Shellie species are going to be available. They aren't exactly common. But if you can find a good LFS, they can usually order some in. Once you start getting into distinct collection points, the price generally goes up (not always, but generally). With that being said, most brevis collection points are going to be a good starter for a beginner. Shellies tend to be quite forgiving with water parameters.
In October 2012, I went in the hospital for spinal surgery (tumor on my spinal cord) and was gone for a week and had no problem with my colony of 4 multis in a 6.6 gallon fluval edge (my colony now lives in a 39 column). They had fry just prior to me being admitted to the hospital. I returned home, but was having severe migraines and the noise from my filter was bothering it horribly (spinal headaches are terrible, noise and light make them exponentially worse, cause by a leak in the spinal fluid). Anyway, I got readmitted to the hospital to have the leak sewn shut and forgot to plug the filter in. They went for a week with no surface movement . While I lost all my fry, all four of my adults survived, and 2 of my largest fry survived as well. Basically, they can survive some bad conditions!