A FACT of life on the farm is is that the cows have to be milked in the morning and they have to be milked again in the evening. Farm families call it "doing the chores." Nowadays, they are getting help from city folks, who are willing to pay for the privilege.

In nearby Lancaster County, Pennsylvania, in the heart of Pennsylvania Dutch country, a number of farmers regularly rent out rooms and cottages to weekend or week-long visitors who want a glimpse of rural America. Over the past dozen years, the list of working farms in Lancaster taking in paying guests has grown to more than 20. A few days on the farm can be a fairly inexpensive family vacation.

"We let them get as involved as much as they like," says Joyce Eby, who with her husband Melvin runs Eby's Tourist Farm, an 81-acre dairy farm with 52 registered Holsteins near Paradise. "They can feed the calves with a bottle; they can feed hay to the cows, and they can watch the milking," which in these modern times is done by machine, though sometimes there's a chance to try one's hands at the old-fashioned way.

Morning milking begins at 5 a.m., but lazybones can catch a repeat in late afternoon.

For many city youngsters, a visit to a farm is their first chance to sample milk fresh and warm from a cow. "It's an opportunity to see that milk doesn't just come from a bottle," says Joyce Eby, who has been putting up guests in the family's 16-room brick house for the past 14 years. The house, built in 1814, has been in the Eby family for five generations. Double rooms rent for $15 to $18 a night, and an efficiency apartment is $30.

At the Landis Farm, another dairy farm just outside Lancaster, owners Earl and Evelyn Landis invite guests to help "make hay" several times during the summer. The hay, food for the milking herd of 50, is mowed and baled by tractor, but human muscles are needed to stack it in the barn. The Landises put guests in a restored 200-year-old stone house next to their own home. With a kitchen, two bedrooms and a private bath, it rents for $35 a night for a family of four.

Generally, the Lancaster-area tourist farms do not provide meals, and those guests whose accommodations do not include a kitchen usually try some of the many Pennsylvania Dutch restaurants in the area. However, at Rocky Acre, the 130-acre dairy farm in Mount Joy owned by Galen and Eileen Benner, morning begins with a hearty "farmer's breakfast": Eggs, homefries, fresh berries, juice and coffee cake were on the menu one day recently.

The Benners, who live in a 200-year-old brick home, can accommodate up to a dozen guests in three bedrooms ($12 adults; $6 for children; breakfast included except Sundays) and an efficiency apartment ($200 a week). Like the Benners, the Ebys and the Landises have children who often are willing to show their younger visitors around the farm.

Many adults, some of them annual repeaters, show up simply to relax and enjoy the country air and scenery. There's fishing in Pequea Creek on the Eby farm, plenty of places to explore by foot near the Landis farm and boating on Little Chickies Creek and horseback riding at the Benners'. Other visitors spend their days (when the chores are done) taking in the Pennsylvania Dutch attractions.

Eileen Benner makes a point of steering her guests to her favorite places near Intercourse, which include the Amish waterwheels along Catstail Road, Lapp's homemade ice cream shop and the Phillip's cheese plant (for Lancaster County swiss cheese).

In typical farm fashion, days can end soon after the sun disappears. "We don't even have a TV set," says Joyce Eby. "There are so many things to do on a farm, families are ready for bed by 9, so they can get up early the next morning."

For more information: Eby's Tourist Farm, 459A Queen Rd., Gordonville, Pa. 17529 (717) 768-3615; Landis Farm, RD 7, Manheim, Pa. 17545 (717) 898-7028; and Rocky Acre, RD 3, Mount Joy, Pa. 17552 (717) 653-4449. Also:

* Brochures on these and other guest farms in the Lancaster area can be obtained from the Pennsylvania Dutch Visitors Bureau, 1799 Hempstead Rd., Lancaster, Pa. 17601. (717) 299-8901.

* The Pennsylvania Department of Agriculture, which has promoted farm vacations as an alternate source of farm income, distributes a 30-page directory describing 25 working farms (dairy, hog, chicken, crop) in the state that take in paying guests. They range from resort farms with such amenities as swimming pool, tennis court and riding stable, to basic farms with spare rooms to rent. Many provide meals. To obtain a copy: Pennsylvania Department of Agriculture, Bureau of Agricultural Development, 2301 N. Cameron St., Harrisburg, Pa. 17110. (717) 783-8460.

* The Virginia State Travel Service (804-786-4484) lists two working farms that take paying guests: The Shenandoah Valley Farm, which raises Black Angus cattle on 155 acres in McGaheysville near Harrisonburg (703) 289-5402, and Jordan Hollow Farm Inn, a 45-acre horse-breeding farm with riding facilities, in Stanley, near Luray (703) 778-2209.

* The 1983 edition of Pat Dickerman's "Farm, Ranch & Country Vacations" lists 200 destinations in the U.S. and abroad. Copies are available from Farm & Ranch Vacations Inc., 36 East 57th St., New York, N.Y. 10022. The price is $10.50 at book rate or $12 for first-class mailing.

GOSPEL FESTIVAL: Jerusalem is the unusual site of a gospel music festival Aug. 21 featuring some of America's leading gospel artists, among them Barry White, James Cleveland, Andrae Crouch, Shirley Caesar and the Southern California Community Choir.

The festival, to be held under the stars at the 6,000-seat Sultan's Pool, an amphitheater in Jerusalem, is an attempt by Israel's ministry of tourism and the travel industry to broaden the country's appeal to Christian and black tourists. An eight-day tour package that includes attendance at the festival is being advertised to 80 churches in 11 U.S. cities.

Promoters, who expect to draw about 1,500 travelers, hope the festival becomes an annual event. An extensive schedule of visits to biblical sites is planned. Departures are scheduled from New York City from Aug. 13 to 17. The price is $1,549, which includes airfare to Tel Aviv, hotel accommodations, meals and five days of sightseeing in motorcoaches.

For more information: International Entertainment and Cultural Group, Suite 1942, 60 East 42 St., New York, N.Y. 10165. (800) 223-1780.

FOOTBALL PREVIEW: The Atlanta Falcons may not be the team of your choice, but they make it easy for traveling sports fans to watch them in preseason training from mid-July through August. Their training camp at the Falcon Complex in Suwanee, Ga., about 15 minutes north of Atlanta, includes a hotel, the Falcon Inn, which is open to the public.

Falcon Inn manager Tommy Nobis, a Falcon linebacker from 1966-1976, says travelers can pull off I-85 and grab a hillside seat overlooking the practice field near his hotel. Crowds sometimes reach 500 or more on an afternoon.

About half the inn's 100 rooms are occupied by Falcon team members and staff during the training season, but the rest are available to the public. The daily rate is about $40. While the players are not readily accessible to guests, occasionally there are opportunities for autographs.

If the Falcons aren't your idea of a football thrill, there is a Redskins connection in Georgia now. The new Falcons head coach, Dan Henning, was an assistant coach with last year's championship Redskins team.

For more information: Falcon Inn (404) 945-6751.

WEST COAST "B & B": California tourist officials say that state is experiencing a "phenomenal" growth in the number of bed-and-breakfast inns. The Office of Tourism has just published a free 40-page guide to 200 of these alternative lodgings, listing prices and amenities.

The inns are grouped by region, which include: North Coast, Lake Tahoe, the San Francisco Bay Area, Carmel and the Monterey Peninsula, Sacramento and the Upper Valley, the Napa and Sonoma Wine Country, the Mother Lode Gold Country, Central and Southern Coast, Los Angeles and the San Diego area.

The inns include restored farmhouses, turn-of-the-century hotels and Victorian mansions, many furnished with antiques.

To obtain a copy of "California Bed and Breakfast Inns," write: California Office of Tourism, Department BB, 1030 13th St., Suite 200, Sacramento, Calif. 95814. Enclose a self-addressed, stamped (37 cents) business-size envelope.