[MarkCole]

If someone had a "sure-fire way" of making an extra $5k a month, I don't think they would be keen to share them.

In my opinion the case market is pretty saturated, and it's a hit or a miss about whether you get anywhere with it, or just lose your money. You say with targeted FB ads you can do it, but you need to get one customer for every $9 you spend, that's not a lot.

If you're looking to start a business, I'd highly suggest building/selling something that you can sell for much higher than $10. More in the region of $100 - $500. The plus side of this if you need to make fewer sales to reach your target.

You have skills that could make you an extra $5k a month and more, that would be much easier than peddling cheap phone cases. Take on additional consulting project for example?

Or optionally, follow the advice of many financial bloggers and simply cut your outgoings to prevent the living paycheck-to-paycheck situation.