I don't know you or the path it's taken you to get to this point. I know what I would do but my situation may be very different from yours.
It sounds to me like they are trying to avoid as much risk as possible. 25 days out of a 90 day 'paid' internship are free? That way they can tell after three weeks if they're going to let you go and they won't be out any money. Maybe they're that unsure about how you'll fit in. Maybe, because they're a startup, they're not even sure if the position you'll be in is needed so this is an experiment to see how it goes?
Your choices are:
accept their terms as they are and hope they like you
negotiate terms so your internship is fully paid
walk away and let them know why
At the end of the day, only you know how comfortable you'd be accepting risk working for free, pushing back in a negotiation, etc.
I know what my answer would be but this is your life and your path to make decisions about.
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I don't know you or the path it's taken you to get to this point. I know what I would do but my situation may be very different from yours.
It sounds to me like they are trying to avoid as much risk as possible. 25 days out of a 90 day 'paid' internship are free? That way they can tell after three weeks if they're going to let you go and they won't be out any money. Maybe they're that unsure about how you'll fit in. Maybe, because they're a startup, they're not even sure if the position you'll be in is needed so this is an experiment to see how it goes?
Your choices are:
At the end of the day, only you know how comfortable you'd be accepting risk working for free, pushing back in a negotiation, etc.
I know what my answer would be but this is your life and your path to make decisions about.