Starting an online business is a good move financially, but you may also have other reasons for wanting to do this. You can choose a niche where you already have some knowledge and experience, or you can search for an area where you are most likely to make some money. This will all depend are your starting point when you come online. If you need to earn money quickly, it may be best to jump right in with something that is known to bring in revenue quickly.
The only thing you must consider in this case is that you may not feel rewarded by what you are doing. The hours can be long the first year you start your online business, so make sure you will be able to stay focused on what your business can do to change your life financially.
Choosing an area that you are passionate about may bring you more joy. If you can translate this into income in a short enough time, this may be best for you. Only you will be able to judge this, because you know yourself better than anyone else.
Some parts of your internet business will almost be guaranteed. Affiliate marketing is one of these areas. As long as you build a list and offer them products and services they want, you will continue to increase your online income.
I recommend doing a little of each; find an area you absolutely love, as well as an area that is known to be a lucrative one. The combination of these two areas will ensure that you enjoy what you are doing while you are also making money online.