Living in Frankfurt as a PhD student

Hello,

I'm in discussion for a PhD position in Frankfurt (medical institute) at most probably a 100% contract. I'm worried about the housing situation and also don't want to spend all of my allowance on rent, which I've heard is booming in Frankfurt. How much can I expect for a studio apartment in a little outskirts as I don't always have to work from office.

Also does someone work in Frankfurt Universitätsklinikum and/or Goethe Institute can differentiate between working at a bigger city like Frankfurt compared to similarly reputed institute in a town or small city. Also some other questions I would like to ask regarding additional benefits, etc for state of Hessen, which I've heard is a little different from Bavaria (where I'm currently in).

Thanks!