The idea of having to take classes over the summer is not the most appealing thing for most people, but if you are behind it is a great way to get ahead. Also if you want to really focus on one class this is the perfect way to do it. Many students stay on campus to take classes, do research, and participate in the mountaintop project, so it is not as lonely as people may think. Lehigh offers a broad range of classes which can be seen at this link. They also offer housing that is relatively inexpensive for $600 per session. That is only $300 per month, which is less than most off campus houses. You do need to have a meal plan to live on campus, but for those who are not that great at cooking this is a good option.
If you are looking to live off-campus many people sublet their homes over the summer. The best way to find out where you can sublet from is to check the class Facebook groups becasue that is where a lot of people post about opening their homes to people who want to sublet for the summer.
If this is something you are interested in it is always a good idea to talk to your advisor. They can tell you what classes would be good to take over the summer, and they can go through your degree audit with you to see where you are at on the path towards graduation.
Additionally, if you are concerned about paying for the classes Lehigh offers the opportunity to apply for government or University loans. The form to be filed out is in this link. Financial reasons do not have to deter you from taking classes over the summer.