These days, you can set up an online business for next to nothing, and be profitable right off the bat - but, as they say, the devil is in the details. Do you have the specialist knowledge and infinite time to spend in setting up a website from scratch, and then making it work i.e. making your online business profitable? After all, you are in it to make a profit, not just to put up online a glorified (and vastly ineffective) brochure for your business.
Neither canyou afford to stumble from one social network to another trying to "connect" with your prospects. If you don't posses the required expertise, you will have to invest time, effort and money to acquire it. Can't be bothered with the code or SEO? Plan to outsource it all? But, how will you know, then, that you are, for example, indeed getting quality SEO service in times when one "wrong" link can wipe out the rankings of years-old websites? How can you monitor your workers and make sure that the goals of your online business are being met? You can't; you will have to get your hands dirty. With an online business, there are no utility bills due, and no rent to pay, but websites need regular maintenance and constant updates.
The critical advantage of an online business is its global presence: the whole world can, potentially, become your client. Since an online store is open 24/7, you can - again, potentially - make money around the clock. However, how do you plan to get your products or services in front of the people? Offline, you can sell them face to face, but online - you must first get them to visit your website. And then, you need to make them trust you enough to want to do business with you.
That is a lot harder to achieve online because of the very nature of the internet. Competition is tough, and the online arena is getting increasingly crowded. On the brighter side, online businesses generally mean lower start-up costs and lower costs of doing business. If you are very lucky, or very skillful, it will also mean passive income to an extent. Your margins are larger when doing business online. Even if you are a one man (or woman) operation, you will be able to present your business professionally. The success of your website depends entirely on you - which is both exciting and scary!