What the hobby cutters can't do is load a roll of vinyl. That for me is a face palm. Rolls are cheaper per foot. The are far easier to manage. I can understand wanting to test the waters. But it is a poor test wadding in the kiddie pool. You just get your ankles wet. If you truly want to start small, at least make a 24" your initial jump point. Then you can load a roll.
But, if you are just really doing this as a hobby, making small items, scrap book cuts, ect., maybe it is ok. If you want to make things in inches thats fine, if you are thinking in feet, get one that can do feet of material. It is not so much the width of the roll, but that it is a cutter that can take a roll can cut 2-4 in lenght times its width. So for a 24" cutter that is 4-8 feet, (maybe better if it tracks well.) A hobby cutter can only go the length of the sheet.