Your mailing list is your market but building up a good list takes time, something which is a problem for new internet businesses that need to start selling fast to generate an income. This is a reason why so many people fall into the trap of buying lists - not only are the validity of the email address doubtful, the huge list will include only a few people who are really interested in what you have to offer. There are no shortcuts to building your own list but there are a few list building techniques like SEO (Search Engine Optimization) that can speed the process for you.
Optimizing your website means that it come high in search results and thus increases the amount of visitors you will have. However, getting people to your site is not the same as their buying from you - this will need a sales effort through sending out sales emails to the addresses they leave with you in return for a freebie. An ebook relevant to your line of business is a great freebie to offer for download because only those who have an interest in the subject will leave their email addresses - and that is a great market for you.
Many people think that splash pages are nothing but an annoyance but they do work - President Obama used one on his website during his campaign and was able to increase his mailing list exponentially. A splash page is simple a greeting page with a catchy headline where people who want to learn more about the product in general (not your specific business - it is too early for that) can leave their email addresses. Once you have these addresses you can use them for sending out newsletters and articles that will indirectly sell your products as well as for direct selling mails.
There is one offline list building technique that is often overlooked. Get email addresses of friends and business contacts for your circle of relatives and friends and email these people giving the reference of whom you got their address from. This will establish a common connection and make to person receiving the mail more amenable to reading it since someone he knows thinks it will interest him.
Remember that list building, even with these list building techniques, is a slow process and building up a list with the potential to be a lucrative market for you is something that can takes a few months; but at the end of that time if you have a good solid list, your marketing problems are over.