My advice would be: don’t do this. At least not for the reason you mentioned. There’s a difference between “starting a small shop” to make some extra money, and having a fun hobby you a getting better in all the time. And maybe sell some of “yesterday’s mod’s” for a few bucks to family, friends or colleagues to keep the cost of being a flashaholic manageable.
Maybe a few extra-ordinary-gifted members could pull off the first variant (selling to make some extra money). The rest of us is lucky if they are not loosing too much money on it. That’s why it is called a hobby.