Neat, congratulations! I know a few people that were active in that space and none of them managed to make it profitable and they all faded out again. It's important that services like these exist and even more important that they are viable businesses otherwise you are building on quicksand.
Well, he said it is his full-time job, so you can safely assume it generates revenue and also you can see they have a Pricing section on their site.
He could have saved up money and be living off of his savings while working full-time, and the amount of money that he is being paid by his customers might be less than the sum of his business and/or personal expenses. Not saying that such is the case here but just pointing out that it's possible.