I took out a loan and had fun between first and second year, and am so glad I did it. you have plenty of work ahead, plenty of time when you have no control over your own schedule, and also plenty of time to arrange research projects, etc. Go have fun. If you are wanting to find a research project, use a little of your time to look for that maybe, but otherwise spend a summer doing as many fun things as possible (remember, this is your last summer off!)
Match Day is still a week away, but I didn't have any problems securing interviews this year.
I went to China with my family for 2 weeks, spent 2 weeks shadowing MDs on an internal medicine externship (and got paid for it), and spent 2 weeks visiting friends and relatives in California. And temped as a secretary/admin assistant at random in between for some cash.
I took 5 year s to get through med school because I traveled for a few months and then did a little research. Few on the interview were interested in my research but everyone wanted to know where I had traveled. It was, if anything, a positive for me. Play now, work later.
I took out an extra loan to spend 6 weeks in Costa Rica, taking 4 weeks of Spanish classes and 2 weeks to travel around the country. I'm soooo glad I did that! I had a lot of great experiences and had a blast. My mom then came to visit me in AZ and we drove around all the big national parks out west. All these experiences were great conversation topics in my residency interviews. They love to see that you have interests besides medicine.
Now that I'm an MS-4 looking back, I realize that there are plenty of opportunities to learn medicine during clinical rotations 3rd and 4th year. But this is the last time for awhile that you'll have 3 months off, in which you can do whatever you want. So find something that you enjoy--whether that be travel, research, sports, whatever--and go for it. Don't feel guilty about not doing anything that's medically-related.
I was a bartender between first and second years, and then went fishing a ton in the off time.....i didn't even pick up a medical book until the day before classes began, and that was just to put it in my bag to take to read the next day! I never regreted this summer, and I was never asked anything about it in any of my interviews.
I did a month-long preceptorship after 1st year, which was good experience, but I would rather have been sitting on the beach. You have TONS of time 3rd and 4th year to learn clinical skills and your vacation time takes a nose dive after 2nd year, so ENJOY IT NOW!