Some of my East Coast interview trips have cost me 300 bucks, and I live on the East Coast! I just bought plane tickets to fly to the Bay Area over winter break, about a month in advance (which can be the typical forewarning that an applicant gets before an interview) and it cost me $600. So the majority of the money that I have spent has been on airfare--it easily surpasses the application fees once you get to the third or fourth interview. Usually once I get to a school, they pay for everything, with perhaps the exception of a taxi here or there.
To echo richardlo, apply to schools that give out early acceptances. Also, I glanced at your mdapps which seemed to have a good number of Midwest schools, which is good. In my anecdotal experience, Midwest schools are more likely to pay for travel. Also, with a few exceptions, programs that are less selective will go to greater lengths to get you to interview. Stay with a host (or a friend in the city, if you have one) wherever you go--there is really never any need to stay in a hotel unless the school pays for it (and it actually precludes you from really getting a feel for student life).
Honestly, as admirable as it is for you to try to do it without your parents help, I wouldn't advise it (of course, that's assuming they have the spare cash to help you out). Think about it, this is the next 7 or 8 years of your life. You might as well borrow a couple grand from them and make sure you get to interview at as many potential schools as possible so that you end up at the place that makes you the happiest.