There is the Pittman Robertson tax to be considered. I'm not sure how the tax is applied, but I did find that a friend who had a shop got caught up in paying a buunch of PR tax on arrows that he assembled in his shop and then sold.
Some of the pro bowyers here should understand how it works.
On the liability insurance, I'd think you should have a liability policy if you are formally making bows for re-sale. If you are simply selling off a few of your own used items, you could still be hit with a liability suit. This is America, anybody can sue anybody for anything! :eek:
If you own your own home, you have a personal liability coverage included in your homeowners policy. You could have coverage there. But, check with your insurance company for specifics.