Well, you can pretty much cycle the money. When you get the profit from bitcoin you can put the portion of it like 50% to spend it to your personal things and then use the 50% of it as an investment again for bitcoin. This cycle will help you sustain the profit and you could save a lot by doing this because you can just keep your salary to yourself if you put bitcoin investment as a part time job for you. In my opinion this is the fastest way and safest to earn money in bitcoin.