How much time should you spend on a side project every day?

I work as a Lead developer in an IT company. My job is difficult, it requires me to put a lot of time on managing my team. After finishing everyday tasks and meetings, I'm left exhausted and tired. I hardly get time to work on the side project. Now, I'm trying to streamline everything manage my time, so how much time should I spend on my side project considering I'm a solo founder and just started off?