Like buying a car, when you go looking for a home computer you're going to find a variety of makes and models -- all of which have optional accessories.

According to computer writer Robert L. Perry, more than a dozen companies make home computers and more than 100 sell computer components.

Among the handiest "plug-in-and-go" makes -- comprising "more than 90 percent of all home-computer markets" -- he lists Radio Shack TRS-80, Commodore PET, Apple II Plus, Ohio Scientific Challenger, Compucolor II, Exidy Sorcerer and Atari 400 and 800.

Newer makes, he says, include Sinclair Research Microcomputer, the APF Imagination Machine Interact models, Mattel Intellivision, Texas Instruments 99/4, Bally models and Hewlett-Packard HP-85.

They differ in such ways as whether you get color and sound, the amount of memory that can be stored, speed of operation, number of characters in a written line, graphics capabilities, and games and other programs available.

Depending on how sophisticated a machine you want, you can expect to pay from about $500 to $2,000 or more for a basic system. The cheaper models are mostly for entertainment and educational purposes. For more complex household management and small-business budgeting purposes you'll probably need a more expensive machine.

In that price range, you get a typewriter-like keyboard package that attaches to your TV set or comes with its own video screen. Also you generally get a cassette tape recorder to store sets of instructions called "programs."

Games and educational programs on tape usually range from $7.95 to $29.50, says Raymond Daly, president of The Program Store at Tenley Circle, which specializes in program sales.

More sophisticated financial programs -- $100 to $300 or more -- are put on small disks about the size of 45-rpm records. To use them, you need a disk drive, which for one make costs about $645.

Printers range from a few hundred to $1,000 or more, depending on the quality of printout.

A telephone modem to connect you with bulletin board or informational services may cost $200.

Says Rob Crissy of Radio Shack's downtown computer center: You buy the basic equipment "to see if you have the interest." Afterward, "You can add piece by piece."