Entry point hardware for profitable mining A) Which hardware
B) Which GH/s level

will be profitable for

1) Pool mining
2) Solo mining

Bitcoins as of February 2014?

Links to sources where information can be checked over time will be great, beyond the simple answer to the questions.
Question is what kind of coin are you going to mine. If you are going to mine Bitcoin (SHA256) you will need special hardware (ASIC 28nm min) for it to be profitable. Here you have an excellent seller, I bought my mining equipment from them, but now they sold out their next generation devices. If you want to mine this coins you will have to risk buying ahead of time, I mean you will have to buy a device that is in development and wait like 6 months for the hardware to arrive, so you will need this calculator to make a preview of what your profits will be. Actually there are many other sellers (Butterfly Labs -which I do not recommend-, Cointerra, make your own search in google, but KNC for me is the most trusted one). Here you have a comparison of mining devices for Bitcoin.

If you plan to mine Litecoin (Scrypt) you will be able to do that with GPUs, you have a mining hardware comparison here.

You will first need to decide which coin are you going to mine and what kind of ecryption are you going to be solving (SHA256, Scrypt). You will need to consider what kind of risk you want to take, for instance, if you mine Bitcoins you know it is the safest bet with an actual price of 803$ and having reached 1150$ per coin it is cryptocoin that is being accepted in stores right now therefore it has a possible great future. On the other hand, mining this coin has become difficult and a considerable investment and risk is needed to aquire the hardware needed.

On the other hand, if you choose a coin which has recently started, it will be easier to mine those coins, but it won't be profitable (if you think that coin could gain value in the future then it may end being profitable, who knows).

Finally it is up to you to read and choose where you want to enter and what amount of money you want to risk.