Are the licenses expensive?
Test fees tend to be $15, sometimes less. Renewals are $8 usually.
Do you have to re-new every so often? How often?
Every ten years. Once you're licensed as long as you don't let your license lapse too long (2 years) you do not have to retest unless you want to get a higher-level license.
Do you have to already own equipment for use/documentation during testing, or can you just test on knowledge alone, and purchase your equipment later?
There is zero requirement to own equipment, either for licensure or for testing. All the questions are multiple choice. All the possible questions and answers are a matter of the public record.
I've been a computer geek at work for many years, but my actual degree is in Electrical Engineering. I hope I still posses the basic knowledge required for a license. After study of course - I have general knowledge of radio from college, but that was not what I focused on, so a lot of that is tucked away in the back of my brain and would require resurrection.
I'm guessing that with your background you could become a licensed Technician with a few hours' study.
Current license levels in the USA are Technician, General and Extra. Technician has good frequency privileges in VHF/UHF and little in HF. General (that's me) has great privileges. Extra has all amateur radio frequency privileges. If you want to be a Volunteer Examiner (someone authorized to proctor the ham radio exams), a General can proctor Technician exams and an Extra can proctor all exams.
Novice and Advanced licenses are no longer available to test for, but if renewed the licenses and privileges are still good.