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!)