As you would not be working in the capacity of a Physiotherapist we could not really tell you what to charge. I would be careful re: insurance and overstepping what assistance you can give, especially for a fee, that relates to sports massage. I am not sure a BSc in sport science qualifies you to treat anything? I might of course be wrong on that. Maybe you should assist in a free capacity until you graduate or offer pre and post massage at what ever is an appropriate charge for that type of service.