If you can negotiate a choice, ask for the lowest number you can get. These channels are accessible to a wider audience because they are on a lower tier of cable access. Most schools already have the basic equipment for broadcasting, but you may need some additional cabling to connect to cable. You can ask the cable company to provide and install this. They may ask you to split the costs, but this should not be a major expense.
Some grants are also available for equipment.
The Federal Emergency Management Agency, for example, offers a grant to channels that air their programming. Others may offer discounted equipment. The channel itself is 24-hour publicity. You can run PowerPoint bulletins of campus and community events. Schedule these at times when your audience is already trained to look for this sort of thing.