This is a part in a series of articles aimed at new people who feel lost and overwhelmed in currently overaggressive cryptoworld. We'll try to make sense out of all of it, together.
In this piece we'll discuss cons and pros of mining and assert if this kind of investment is a good fit for you.

Investing!?

Yes! Long time ago mining bitcoin was something done for fun in a spare time. Nowadays you can fully classify it as an investment or business. The concept is really easy to understand: you buy special equipment which generates profit overtime.
Mining has strong pluses:

It is a relatively low-risk investment. If anything goes wrong, and alas life is unpredictable, you can try and sell your equipment.
It is a relatively low-risk investment. If crypto goes bearish (meaning it loses in price), or the coin you've been mining goes down, it affects your portfolio but not in an extremely dramatic fashion.

These points also make sense:

You become a backbone of blockchain. You start mining cryptocurrency and it is liberating. And fully legal. In fiat-world only central banks do something similar.
You engage with the community more. You get to meet a lot of new people, you get to know a lot of things you ignored before.
This is an easy bootstrap into crypto. You will have incentive to find the most profitable coin and to do that you'll try and learn a lot of different projects.

As an investor into mining your prime goal is to make a return on your equipment(investment). We refer to it as ROI. Once you ROI'd, you are essentially generating free money! Cool.

However mining has strong minuses too:

Slow ROI. This is very, and very relative. At current retail prices we can assume about 260~ day ROI (feel free to play around with it here. All credits to SerfyWerfy!)
I don't know where you're from, but in my place a yearly return on investment is considered extremely good.
Bearish views on mining. Essentially mining is a wasteful endeavor. We spend a lot of electricity and manufacturing power on it. Many people are opposed to it because of potential damage to ecosystem. There are active alternatives to mining protocol being developed and tested.
It is worth stating that it is not true currently. Mining is still minuscule, even at current level, and amounts to tiny bit of wasted resources. However eventually it could grow into a big concern for whole planet. We folks in crypto are responsible like that and like to think about future.
Tech requirements. You have to build and maintain your mining equipment in operable conditions. Don't be scared though, it's not that hard, there are already tons of guides out there and I'll walk you through them too!
Mining is versatile but not completely versatile. Coins like Bitcoin are dominated by ASICs, special systems which sole purpose is to mine given algorithm. This means that in a case of a new and better ASIC coming out or Bitcoin plummeting in price you'd be left with useless piece of equipment. In the spreadsheet above I've given you're looking at GPU mining, a safer alternative because there's an actual market for videocards (gamers, graphical designers, researchers).

Wow, that's hella lot of minuses!

Correct. Crypto is not a fairy tale; it is a highly competitive field growing at an alarming rate.
You have to be aware of risks.
So, to rehash:

Mining is relatively safe. It won't be gone in a day. You can mix different ASICs & GPUs and diversify.
Relative to contrary belief it is not plug-it-and-forget kinda thing. You will make more if you're actively chasing coins and following trends. It is completely possible to automate it though: I haven't touched any of my mining rigs in 4 weeks. They still generate profit but if I were active I'd be making 15-20% more.
It does require a setup. Electrical grid, wall outlets, assembling, ventilating. That requires a decent amount of time especially on your first one.
It is a slow investment. Imagine finding a coin you believe in, ordering and setting up your miner only to have that coin moon(dramatically increase in price) few days later. You'd make a lot more by just buying it directly!
It's hard to scale for big investors.

So, this is supposed to give you more or less fair overview of mining as it is. There are other investment options in crypto.

Bonus rambling and speculation

A lot of miners are currently unhappy with ROI. It is expected and projected that over the time more and more equipment will be directed towards mining. The more people are mining, the less each individual miner gets. So it is not wise to take 260 day ROI as a baseline. If conditions stay the same ROI will decrease. You'd probably want to think more in 350 day territory. However if you're active and vigilant it is totally plausible to ROI in 6 months.
There are some good news though. Ethereum is about to implement Metropolis which will increase mining rewards by ~25% in the mid of October (16th). This means that there's more money for each individual miner on the market -- some will switch to eth leading to mining profitability increase over all GPU algorithms by ~15%. There's also an interesting bitcoin fork called bitcoin gold coming out at the end of October (25th) which attracted all sorts of controversy. It could still prove to be a successful coin since as far as I know apart from withholding information (which is kinda shitty) developers never really tried to straight out lie or scam anyone. If this work is a success we will see yet even more income overall for GPU miners. So all in all whitest mining is not a get-rich-fast scheme anymore, I'm still very bullish and confident in it.