Scott, A good rule of thumb is to never purchase a house if you cannot afford the payments on your salary alone. It's great that you have 2 roommates now, but what if they decide to get their own place? disagreement? You are taking the right steps to ask before you react. Next step is for you to speak to a mortgage lender, get pre-approved based on your own income and stay within your budget.
A good mortgage lender will not let you do an ARM loan nor an interest only. Interest only loans are for people that are expecting to cash in on something big in the near future.. are you? may be expecting a hefty inheritance? or other?