Working at home with your own online business is no no different then an offline business when it comes to reinvesting. You won't be investing as much as you would with an online business as you would an offline business, but you do need to put something into it. It may be investing in advertising, hiring an SEO expert, hiring a marketing expert or anything. Sometimes you need to hire a writer to write great articles for you. Another author would not be emotionally attached to the business and may give your articles what you need! You should put something back into your business as you start to profit. It will (not might-it will) allow your business to grow.
I wish I had realized how important this was in the beginning! I would have saved myself some long drawn out grief. Not that business was horrible in the past, but I grew drastically with reinvesting. When you start to profit with your business, seriously consider reinvesting some of the profits (not all of the profits.) You will see success with your online business.