Career change and internships.

So I'm currently undergoing a career change and since my job requires no degree I never finished one. Now I'm currently working on finishing my degree, but I'm not sure what the "protocol" is on summer internships since I'm gonna be an old man in the IB world. My goals are to finish my 4 year and apply for an MBA, but will I be able to get work experience by applying for SA positions or will I be too old for it in my late twenties?

I know that banks hire Associates through their thirties but do people expect work experience via SA when/if you're finishing your undergrad and do people intern when they're in b-school?