This is a question that bugs many a newcomers to blogging. The ease of which one can create and maintain blogs these days, no wonder people try their hands at several when they have multiple topics.
However, it is usually best to focus on one blog — particularly when starting out — and giving that blog a clear focus. Blogging requires a lot of time and energy, and dividing this among three or five different blogs is the fastest way to burnout.
The majority of the big-name bloggers have one blog. A few have found success with two or more, and even then most of these with multiple blogs rely a lot on guest posts.
Speaking of which, if you have expertise or interest in other areas, you can still write about them without running multiple blogs. Guest posting on other blogs is the perfect avenue for this, and if you can somehow tie the topic with your original blog, you have a win.
Fact is that it is quite tough to really grow more than one blog at a time.
You will have to maintain separate social accounts for each (Facebook, Twitter), regularly post on each blog, and then promote them. Reaching the glorious milestone of 1,000 subscribers is quite a task — now think about doing that times three.
And chances are that if you find success with your first blog, it becomes a hit, starts attracting a huge audience, inviting guest posts as submissions, then you can easily focus on launching your next success.
Having said that, starting with a single niche blog may not always be the optimum thing to do.
There is the case of putting all eggs in one basket, or your monetization strategies might require different platforms, and in the fickle search engine environment of today, there is always the chance of messing up and incurring a rankings penalty.
But if you can afford to start up with one blog, always go for it. It comes with its advantages.