Here is a few things I've learned that you should be aware of:
1. FB is very time consuming. You have to respond to FB e-mails from followers, respond to comments, and be on top of what's going on 24/7.
You also have to constantly create and find new content to post. This is incredibly time consuming. Try posting 3 or 4 viral posts a day. That's 21-28 times a week. That's a lot of work to get so many posts that will be home runs.
There are only so many memes in a niche. So then you have to create some - and let me know tell you, it's quite a learning curve to create viral posts from scratch. And it's very time consuming because you're basically doing graphic design and copywriting. And you have to create fresh content the next day, which means the same design/"look and feel" can't be used over and over.
2. It's not scalable. CPA/PPC aside, FB is hands on all the time. You have to consistently find new content. That requires sitting on your butt all day long searching for and creating viral content.
3. FB's algorithm is evil. Great, so you got 10k fans, guess how many your posts will reach? Only a small minority of your followers. So now you have to pay for promoted posts to reach them all.
4. Non-monetary feeling of success: this is where clients of mine end up getting deflated sometimes. They start off feeling great that engagement skyrockets and they're getting new followers. They feel like people love them. Then all of a sudden they realize that many of those followers have no interest in buying their product or going to their links outside of FB. So be careful of that initial feeling of euphoria if there's no $$ coming in.