My family has a lot of military folks in it, but my information is dated. The way I understood it is that the Citadel is a state school so unless your friend is in state, it is not inexpensive. The cadets there do NOT get automatic ROTC scholarships though they may all be required to take ROTC as part of the program. There are opportunities to get ROTC scholarships even if you do not get one right out of high school but they are not automatic. I don't know if the Citadel, VMI and those other schools that are military in the way they run things have an inside track for the ROTC awards.
The bottom line, though I am not postive, is that your friends are going to have to come up with a substantial amount unless they get financial aid from the school. I don't know if the Citadel guarnatees to meet full need.
It's touchy going into these subjects with even close friends. I worked with our cousin this summer, and it was a lot more delicate footing dealing with those issues than with strangers. My close friend whose son went Air Force ROTC was was given info by her son fraught with misinformation but she didn't want to hear it from me. It wasn't until she had to pay the bills, they were in her face before she believed that she would have to pay for pilot's training out of pocket---not included in the university tutions or ROTC. Nor did she believe that her son was not going to get an automatic pilot placement as an ROTC graduate with an Aviation degree. I knew better but pushing it would have caused problems.
So, unless things have changed, going to the CItadel without getting ROTC scholarships which is a competive and arduous process that a senior has to undergo with all other seniors unless they are going to a military academy like USMA, USNA, USAA, CGA< MMA--there may be a sixth, can't recall, but certainly NOT including the Citadel,it costs just like any state school and charges room and board, and the student has to apply for financial aid and hope to get merit money.