Hi Emily
First of all, you need to calculate your actual net income from Airbnb. If you make $1000 from Airbnb, you also will have expenses you can deduct from that. First, make sure you deduct the 3% fee Airbnb takes from hosts -- because when they report your income to the IRS, they do not deduct that. You have to deduct it as an expense. Then, other expenses are, utilities, a portion of your rent, and any supplies you purchase for guest's use, etc. You would need to keep receipts for all those expenses. Then figure your net income.
The amount of taxes that you will need to pay on your Airbnb income, depends upon how much other income you earn during the year. Your Airbnb income is added to your other income, to create a total income figure. Then you will pay tax based on the tax rate for that income level. So, your tax on your Airbnb income is totally dependent upon your other income -- and same for your roommate.
Here's a website that has tax brackets showing on it.:
http://www.efile.com/tax-service/tax-calculator/tax-brackets/
and:
http://www.forbes.com/sites/kellyphillipserb/2013/10/31/irs-announces-2014-tax-brackets-standard-ded...
So for instance, if your other income was $35,000, and your AIrbnb income was $500, your total income would be $35,500 and you would have to first deduct the standard deductions that IRS allows, which change each year. For instance, in 2014 the standard deduction is about $6200 and the personal exemption is about $3900. So together, about $10,000. THat means that your taxable income is then about $25,500. The tax rate on that income level is about 15%.
You should consult a tax preparer to make sure you take all the deductions you are allowed to take, to minimize your taxes, and to get help doing the taxes if you aren't comfortable doing it yourself.