There are many things to consider, just make sure you think it all through, before you start, to make sure you can do it.
For me, the biggest surprise was how much I really had to put up to get started.
I had a sewing machine, so that was a start.
Then I got a serger. Then I needed material for diapers. Not just one kind, but I wanted velour and sherpa in many colors, I wanted knits and wovens, etc etc.
Then I needed little stuff like elastic, thread (for sewing machine and tons of wooly nylon colors), etc.
Oh wait, I needed labels too, and a snap press, and snaps in 50 million colors.
Then I needed a name, a website designed, the cart setup, web hosting.
I already had a digital camera for the pictures, so that wasn't an expense.
Also, I had to invest in shipping supplies (envelopes, labels, etc).
Extra printer paper and ink for invoices, etc etc etc!
It was just a lot more of an investment than I thought it would be.
Sure, you could do aplix and get by with a few fabrics --but I wanted to do it RIGHT, and have fun variety, etc.
So anyway, that's my experience with starting up SugarPlumBaby.com! I don't know if I'd do it again, but now that it's running for 2 years now, it's not too hard to maintain.
Oh, and another thing that drove me nuts was perfect my patterns! I finally have them all as good as I want 'em! LOL