Does the word "big" seem to dominate your life? When you think of "big" do such terms as "mortgage," "house," or "Dolly Parton" come to mind? When you hear someone discussing the national debt does it remind you of a heating bill?

If the cost of owning a house is getting you down, remember that many people haven't reached the point where they can afford a mortgage in the first place. Some of these very same mortgage-less individuals may be willing to share your financial burdens.

From Sherlock Holmes to Arthur Fonzarelli, renting out part of a home has attracted a variety of boarders. Becoming a landlord may not be a bad idea, particularly now when good rentals are increasingly scarce and the general economy has been struck by "reflation" or "incession" or whatever it is that causes grown men to hoard pencils and eye street corners nervously.

Increasing numbers of homeowners are bound to become landlords, at least in part. Why? Consider these trends:

Homes are more expensive. In 1969, according to the National Association of Home Builders, the average new house cost $25,600. This year the average will top $64,000. Not only are prices up, but the cost of money has risen as well.

Families are smaller. The Census Bureau reports the average household contained 3.37 people in 1950. By 1978, the figure had dropped to 2.81 individuals per household. Somehow we have lost over a half a person per housing unit.

Homes are bigger. The size of the average detached house has gone from less than 1,000 square feet in 1950 to over 1,750 square feet in 1977. A study by Rutgers University says the preference for larger housing units has been incorporated in many zoning laws -- in effect requiring us to buy bigger homes.

The result of these trends is that many of us are over-housed. We have more space than we reasonably require or have time to clean. Having a tenant can make sense.

The path to finding a good one begins with your home. Is there some part your house which is rentable? Ideally, it should be an area which gives both you and your border privacy. A basement or attic can work particularly well since territorial boundaries are clearly defined.

If possible, the tenant's portion of the house should include a separate bath and kitchen, plus enough space for friends, hobbies or work. A separate kitchen, however, is restricted in most cases by area zoning laws.

Habitability is also important. Would your rec room make a good rental area? Does it double for a meat locker in January? If so, the probability is that even the most energy-conscious tenant would object. Before putting part of your home on the market it pays to insulate, upgrade, paint, and caulk. pSmall touches, such as curtains, also help.

How much you can charge depends on the competition from nearby efficiencies, one-bedroom apartments, and houses to share. Check the classifieds for pricing guidelines.

Once your property is advertised, generally in the classifieds under "apartments, rooms, or houses to share" or "furnished rooms," you will discover many possible tenants.

Will you accept a student or require someone with a visible means of support? Will you permit children or pets? Would you object to a smoker in the house?

There is no sure method to determine whether an individual will make a good tenant. It can help to speak to employers and present landlords. Even here the quality of information may be suspect. For example, a current landlord may give a glowing endorsement of a tenant merely to get rid of him. It does help to have a long conversation with your potential boarder. If possible, visit them at their current residence.

After you find a tenant be certain to get a deposit equal to one month's rent. Also, install -- or have the tenant install -- a phone in their name. If there are disputes concerning long-distance phone bills it is then a matter for the tenant and the phone company to resolve, not the homeowner.

In somes cases you may want to trade house work, baby sitting, or whatever, for rent. One way to do this is to change the month's rent in cash and then calculate a fee per hour for tenant services. At the end of the month the tenant gets a rebate, the size of which depends on the number of hours worked.

The income from your tenant is taxable, but the portion of the home used by the boarder can be depreciated. Also, you can deduct the proportionate value of utility costs, mortgage interest payments, and general repairs represented by the tenant's area of the house.

If yours is one of the many households in the Washington area that has extra space -- habitable space -- then perhaps you should consider a boarder. Having a tenant will not make you a member of the landed gentry, but it will offset some of the burdens of homeownership.