1. Look up average starting salaries for recent college graduates with your college major in the city you want to live in. Be sure to account for taxes, which will probably take between~15–25% of your headline salary depending.
2. Find a student loan calculator. Play around with the variables (interest rate, principal amount, etc) and see how much the monthly payments come out to.
3. Look up the cost of living in the city you want to live in. Take a look at that city’s Craigslist room wanted/rentals section to get an idea how much people are paying to live in that place.
4. Create a mock budget that includes your expected earnings, rent+utilities, food, shopping and entertainment, rent, and student loan payments and see if you think you can live with that.

Or you can just wing it. That’s what most of your peers will be doing, at any rate. At the very least, you should look up the student loan calculator and see how much your monthly payments will be.