How to design the equity distribution among the team?

Hi,

I'm planning to start a new project and managed to gather a bunch of engineers and domain experts to work on this together. What puzzles me is how should I split the equity among us. I'm currently working full-time on this idea. All other people can only contribute in a part-time manner. We haven't started to raise funds yet so none of us gets any cash compensation. I am planning to pay for any potential infrastructure-related costs moving forward to support this idea. Is there any concrete advice regarding this kind of scenario? Btw I'm also not sure if I need to worry that people might just download a copy of the code base and leave the team once the core service is built. I know these are dumb questions but I do have to ask since this is the first time I start a company with other people.