====================For Master Degree holder ====================
I will not recommend you to join IB as GD 11 if you have education level up to master degree. The alternative way is to join IB through FPSC in BPS 17/BPS 16.
Following are the reasons.
1. The job is below the level of education you have.
2. You have to sign a bond under which you are not allow to join any other organization. Due to which you are not allow to apply for any post even through FPSC General or FPSC CSS.
3. Promotion structure is not so fast you can get maximum up to BPS 16 after 25 to 30 years of services. Where as you can join directly in BPS 17 / BPS 16 in any other organization.
4. There is no accommodation available. You have to live on your own in which ever city you are posted.
5. You can be posted to any remote location in and outside Pakistan.

====================For FA/FSC Level ====================
I will recommend you to join IB in GD 11 for the following reasons.
1. It is one of the best job for FA level student except the commission officer in armed forces of Pakistan.
2. The training in IB will improve your education and physical abilities.
3. There is 20% Allowance in salary currently which is RS. 2,514 if your basic salary is RS. 12,570.
4. With in 25 to 30 year of service you will be promoted up to BPS 16 which is consider a good scale of a person having qualification FA/FSC.

Is the accommodation issue the same for BS-17 officers?

Yes same goes with the BS-17 but the salary is higher then normal BS-17 e.g (BS-17 Lecture salary plus 15 to 20K) so you can afford your own accommodation