Yes, you can mine solo, but if you start with just miners that do not generated enough hashes, you will end up not getting any mining reward. You will need to buy thousands miners that will cost you billions in dollars in order to mine solo.  But, if you think you will mine solo at home with some GPU or ASIC and think you will get reward, if it happens, that mean you are lucky because the chance that you wi get a single mining reward (6.25 btc) is less than 0.001% because of the mining difficulty of bitcoin which is very high. Even if you use billion to set up mining farm, you will still want other small miners to join you, that is how the business work which will still result to mining pool. Gone are the days of mining solo.