If you’re building everything on your own (sounds like you are), it doesn’t matter if they came up with the idea, if they already have designs and mockups, and if they already have potential customers lined up.
The minimum you should look for here is 30-40%, and even then you need to ensure they’re doing a few things, like actually putting in some of their funds into the launch (bootstrapping is fine but you still need some $ for domains, hosting and server costs, and some initial ads), and spending just as much time if not more time than you on getting sales, customers, and market research as you are coding.
If you’re building everything on your own (sounds like you are), it doesn’t matter if they came up with the idea, if they already have designs and mockups, and if they already have potential customers lined up.
The minimum you should look for here is 30-40%, and even then you need to ensure they’re doing a few things, like actually putting in some of their funds into the launch (bootstrapping is fine but you still need some $ for domains, hosting and server costs, and some initial ads), and spending just as much time if not more time than you on getting sales, customers, and market research as you are coding.