My eldest is in her second year at Purdue and my youngest is considering Purdue when she graduates High School (which I would like since I now know my way around campus!).
My suggestion is to visit Purdue when it is in full session, not during the summer. We toured during the summer, and some things, like parking, were much more open then than when my daughter actually started school there. Here we were thinking she would have no problem when she brought her car down the following year, but no, parking during the school year is tough!
Also, ask about the English-speaking skills of the teachers/professors and teaching assistants. My daughter has had two professors and two TAs that had terrible English skills and were very hard to understand. Purdue does pride itself on having a broad range of professors that are highly accomplished, but sadly that broad range includes those that have a very hard time with English. I was not happy that my hard-earned dollars were spent on building up Purdue's status in number of professors with no focus on their ability to teach the students.
Those two complaints are my only real complaints though! My daughter LOVES Purdue! She feels safe on campus, the food courts are fantastic, like a buffet everyday, she liked her dorm well enough, and the bus system is very good.
If your son is interested in maintaining a spiritual connection, there are buildings right on campus that house churches and college youth groups. My daughter is involved in the Methodist group, and is presently in the Methodist housing off-campus. This is a better fit for her than the dorms, as she was not one to enjoy the atmosphere of dorm living in her freshman year. She just isn't a drinker or one that likes to party late into the morning. I suppose at any college, there is the party atmosphere in the dorms, especially amongst the freshman. It was nice that there were other living options available after freshman year.
There are many, many clubs and activities at Purdue, so if your son wanted to get involved in a group outside of studies he should be able to find something.
One of the things that really sold my daughter on Purdue was interviewing the head of the department in the major she was interested in. If you know when you are going to visit Purdue, I highly recommend trying to set up an interview ahead of time. We visited many schools when looking at colleges, but as soon as my daughter met the head of her major, she knew Purdue was it. Not only did he give her a tour of the whole department, and introduce her to the other professors and teachers, he also had her meet the office staff and assistants, so she could feel more "connected" and see the people that would be there for her if she needed their help.
It also helped that he mentioned different internship programs that he had sent students to, including Disney. Her goal has been a Disney internship, and she felt Purdue would help her get there. In fact, she is at Disney right now doing her internship!
Purdue really loves its sports, and being a Boilermaker as opposed to a dog or cat (we looked at UGA and UK too) fills the students with a great sense of pride. If you ever plan on going down during a game, know that there is not that much available for hotels close to campus near game day, so make your reservations months ahead of time. I realize other schools have great pride in their teams too, but just wanted to let you know that so does Purdue!
If you have any other questions, let me know (I will try to check back later today). I know that a few years ago, when we were looking at colleges, there were other people on here that answered our Purdue questions, and if they are still here I am sure they may have more information for you than I do, but hopefully you have a start now on your Purdue search!