You must have a work/resident permit but in certain circumstances, they accept to open the bank account without it.
I am with Société Générale, excellent services.
You can have loans, but not on extended period as in Europe. Rates are crazy, like 12% in USD and 30% in cedis.
Take a bank with lots of ATM's in the country, there is no interconnection between the different banks and all of them have thei own system, unless you use visa, but you are very often doubled debited.
Best is to take an account with the agency close to your office/residence and take enough cash for one week / one month.