i think Bitcoin is only profitable if done at large scales. you must get expensive mining equipment and of course it consumes a lot of electricity monthly. Also its usually much more cost effective to buy Bitcoins with this money instead of using it to buy mining equipment.
That's indeed the problem so I really do think that bitcoin investment is a much more efficient way to earn Bitcoin that mining. In mining you will need to have expensive equipments or computer amd in addition with that is the electricity bill and interner bill. It will be surely costy and that is where problem would be generated from. Also read more informations about it if you are really interested into mining.