Help with my 27 y.o. Son

Hi Brooke,
My son who lives away from home frequently calls us asking us what to do about not having insurance, not being able to pay his rent, having too much school work so he can’t work, anxiety, etc. He has problems with self esteem and is very past focused and does not trust decisions he makes due to perceived failures he has had in the past.
My question is what do we tell him when he asks what should he do? I have tried to say, what do you think you should do or I am confident that you can figure it out but he just gets mad and hangs up. Maybe he wants us to offer money but we have already paid for his rent for 9 months of last year plus more.
One phone call he does not want any more help from us and then next is with a financial crisis. We want to set some financial boundaries with him but have had to co-sign on apartment leases because he is a personal trainer and has his own business and does not get pay stubs. We are worried if we co-sign again he will automatically assume we will pay the rent. We want to save for retirement and not feel resentful towards our son. How do we do this from love?