Hi ChrisSpencer,
Glad to know that you are thinking of starting your own venture! Though it is a very tough job and there will be a lot of naysayers, it is important to be focussed if you want to make it on your own. After all, you will be facing a lot of challenges on the way before you even have the first taste of success.
Before you even begin, it is improtant to first zero in on what you want to invest in. It has to be something you have knowledge or the interest in. Starting a business is a huge commitment and you have to do it for the right reasons, or it will be easy to falter. Persistence is the key word.
The amount you would need to invest would be subjective depending on the business you decide to go into. Finally, it is important to provide an edge to your business, which can be done only if you understand your market. After all, you need to have a product/service which the customer wants.
You are definitely on the right track because some of the impossible feats have been started off by asking a relatively naive and stupid question. All the best to you!
Regards,
G