The real question is, what sort of business are you running, or planning to run.

Are you thinking of becoming an affiliate marketer? In which case, you could run your business without having your own website. Plenty of people earn loads of money online by promoting other people's products, and you can do this by using advertising, either classified or pay per click. By article marketing, in fact a whole host of methods.

Gain Credibility.

A website of your own can give you more credibility when recommending affiliate products. Don't have a site full of ads and affiliate links, but one which gives your potential customers good solid information about you and your company. Contact details, maybe a little history of your business, why you're in this sort of business. People buy from someone they know or at least someone they like. Help them to know you.

Build a customer base

Having your own website means you can put an opt-in form on a page for people to subscribe to a newsletter or special offer, something to get them to give you their name and email address. That way you can build a list of customers with an interest in your type of service or products. Without a list you are continually looking for new customers. Remember money is made from a sale. Fortunes are made from back end sales. You need to keep selling to these customers time and time again

Pre selling

Even if you're selling affiliate products with a great site of their own, having people visit your site first gives you the chance to pre sell or warm them up. You don't need a 10 page sales letter. Whet their appetite, don't bore them to death. Most products are a solution to a problem. Explain how your product or the one you're promoting as an affiliate will solve their problem. Point out the most important benefits. Get them into a frame of mind where they want to find out more. Then direct them to the sales page or site.

Multiple Income streams.

If you are promoting more than one product, either your own or as an affiliate, than having your own site can give you're a sort of base camp to tie things together. You can have links to pages for different yet similar products. And if the pages are filled with useful information rather than just advertising, your visitors will have a more rewarding experience and hopefully be more likely to buy, and to recommend your site.

Additional Income

Don't forget that having your own web site, gives you more opportunities to earn money. AdSense for example. Now some people will snort derisively when you mention AdSense, but it costs you nothing to put it on your web pages, and it provides adverts targeted at your market. If someone clicks on an AdSense ad on your site and then buys from that advertiser you earn money! It may not earn you a fortune but why should you turn it down.