Before moving from on campus housing to the off campus apartment upgrade, there are some things to consider. The first one is cost of rent. In most cases, the off campus apartment will be cheaper per month. However, you have to consider that when renting an apartment, you will be signing a full year lease. Therefore the rent of an apartment will be for 12 months, instead of the 6-7 month term that an on campus dorm would be. But if you are going to college year round, the apartment will probably be a better value. The more roommates you can sign the lease with for an off campus apartment, the cheaper your rent will be.
Another thing to consider is the cost of utilities for an off campus apartment, such as heating, hot water, electricity, internet, and cable. With the college dorms, all of this is included, so you will have to factor in utility bills for the off campus apartment. Rates are different for every town and city, so ask your realtor what the typical utility rates will be, and what you should expect for a utility bill.
An additional aspect to consider when comparing on campus housing to off campus apartments is convenience. On campus dorms will be a closer walk to all your classes and all your friends, if they are staying on campus. If all your friends are staying on campus, you might get a better social life if you continue to live on campus. If you have to drive from your apartment to your college, it will be more inconvenient to visit your friends or have them come hang out with you. But if you live in a big city where everyone can walk and take public transportation, then the social life will be about the same either way. Friends may be more inclined to hang out at an off campus apartment than cramming in a small college dorm, depending on your college.
One aspect that makes it very difficult for people with limited means to get apartments is the advance deposit. Before signing the lease for an apartment, you will have to pay your first months rent, last months rent, a security deposit (which will be refunded when you move out), and realtor fees (corresponding to one months rent). A typical apartment deposit will be four months rent in one lump sum. This will be easier to handle if you are splitting the apartment deposit with roommates.
One final aspect to consider when comparing on campus dorms to off campus apartments is the landlord verses the school. The school will accept the entire housing payment for a semester from your student loans, even if they do not distribute to your school until later. However, your landlord will not be as flexible, and will expect an on time payment every single month. Therefore you will have to have the cash in your bank account in advance to pay for rent. If you do not have the money, you will have to find a student loan that distributes directly to you instead of your school.
Both on campus housing and off campus apartments have their pros and cons, so you have to evaluate your own financial situation, and what would work best for you.