The cost of enrolling in a telecourse varies with the college. At Prince George's, the charge is $22 per credit for county residents. The fee is $87 per course at Montgomery College. At the University of the District of Columbia, $53 for a three-credit course. For Virginia residents, $15.50 per credit hour at the Extended Learning Institute of Northern Virginia Community College.

To attract students, Channel 26 is previewing the five courses on its schedule this fall, with a half-hour introduction to televised education, "Learning by Viewing." A phone hotline will be available to provide answers to questions on registration.

On Saturday, "Learning by Viewing" will be shown at 1 p.m., with previews to follow of "It's Everybody's Business" (introduction to business, 1:30 p.m.); "Personal Finance" (2 p.m.); "Issues in Child Abuse" (2:30 p.m.). On Thursday, Aug. 19, "Learning by Viewing" will be repeated at 10 p.m., with previews of "American Short Story (10:30-11:30 p.m.) and "Issues in Criminal Justice" (11:30 p.m.).

The Maryland Center for Public Broadcasting will be offering courses through 20 Maryland college. They include classes in American history and government, Shakespeare's plays, "It's Everybody's Business," "Making It Count" (introduction to computer usage), and two psychology series, "The Growing Years" and "Understanding Human Behavior." For information: Maryland Center for Public Broadcasting, Maryland College of the Air, Owings Mills, Md. 21117, or (301) 337-4038.

Northern Virginia Television, Channel 53, will show courses on the principles of data processing; "The Growing Years"; "Topics in Small Business Management"; history of American art; a photography appreciation series and "Keep It Running," a consumer auto-repair class. For information: Extended Learning Institute, Northern Virginia Community College, 8333 Little River Turnpike, Annandale, Va. 22003, or 323-3371.

Also, contact the college of your choice for more information.