IF YOUR MOTTO is, "I spend, therefore I am," then Cambridge is the place to be. On your trek from the River to the Yard you can pick up a squash racket, poetry by an obscure author, and a slice of pizza with hardly a break in stride; when you tire of the Harvard market you can hop the Dudley bus for a quarter, and pour your green from Central Square to Roxbury.

The Dudley route passes through streets lined with small merchants, one-room boutiques as well as cuchifrito parlors, whose size may spell chic to the shopper but struggle to the owners. If you're on the bus you can pick and choose from the multitude of storefronts, but behind each is an owner who spends six or seven days a week there, 52 weeks a year. Often the owners are the shop's only employees, working 12 hours a day and worrying the rest. In spite of their labor, roughly a third of these small proprietorships go bankrupt within a year after they open and another third closes within five years. The mom-and-pop merchants try again and again, however, anxious to feed, clothe and bejewel us in order to nurse their infant stores along, maybe hoping that their progeny will remember the favor and take care of them when they retire.

Sid and Louise Gerstenblatt just opened their baby eight weeks ago, at 988 Mass Ave opposite the Orson Welles theater, and they have high hopes. Originally from Montpelier, Vermont, they are the Grandpa and Grandma behind "Grandma's Cookie Factory," which is the retail branch of the wholesale cookie business they ran in Montpelier along with their son Jeff, and friend of the family David Peatman. Grandma's offers six kinds of quarter-pound chocolate chip cookies, carrot and other cakes, bagels, and "what we're going to do with ice cream," says 38-year-old Sid, "will blow your mind."

The Gerstenblatts entered the cookie business in 1973 when they moved to California in search of more interesting jobs. Trained as a social worker and possessed of a degree it took him ten years to earn, Sid resembles everybody's Jewish grandfather, with his shock of white hair, and grey eyes framed by sensible glasses, except for the "groovyisms" of this year and last with which he sprinkles his speech. He designed a non-profit dental program in Vermont and health center in Rhode Island while his wife worked as a nurse and a consultant.

One day, Louise baked a few cookies as a favor to a storeowner friend who sold the whole batch within two days. That gave Sid an idea. Operating out of one kitchen, Sid, Louise, Jeff and David started Grandma's and began to sell their wares to small shop owners in the area. Within two years they were selling cookies to stores throughout the country. Now the Vermont business employs a staff of five, and has a $200,000 volume of business.

As the Vermont plant prospered, Sid and Louise decided it was time to expand, and they looked for a place in Cambridge because, "Frankly," says Sid, "I hate Vermont. Cambridge has the Orson Welles, Chinese food, diverse people--besides, it's near the beach."

The Gerstenblatts and Dave see further growth potential in their business--they have plans to add pies, ice cream, and even a pizza-sized cookie to their line of quarter-pound, two-pound, and three-pound cookies. Dave thinks the business could sustain a series of franchises throughout the city and in other states. But what is most important to the Gerstenblatts is that the business is theirs.

"I have a G.S. 13 but I've never used it," says Sid. "Louise said to me, 'you know how long you would last in a bureacratic job? About two months.' I'd blow up the place. Besides, it's a happy scene, it's not a pressure thing."

Son Jeff, who quit the graduate program in international affairs at American University to help out Grandma's Cookies, adds, "I'd like to make enough to be comfortable but I can't work for a boss at the State Department." David, who has participated in every step of creating Grandma's from baking to marketing, also says, "I feel like a part of it; I'm not just working to make someone else money. We have to work hard up in Vermont, but it's not an assembly line."

Small-scale capitalism still has its contradictions for this social worker-cum-entrepreneur and his Berkeley graduate son. His face animated, Sid says he feels "caught between what I want in life and what I need, and what I want to do for others. I'd like to be involved in a social cause, I'd like to make sure that the needs of the elderly get taken care of. I'd like to work to change the system, but I'd be knowing all the while that it's virtually impossible to change it."

Like his father, Jeff believes in capitalism, and he feels his most important task is improving his life without stepping on people--just trying to be a decent human being. "We don't," he says, "push high-priced stuff that people can't afford."

Sid is even more convinced that Grandma's is the right choice for him. "I've paid my dues for ten years," he says, "and I've been a hustler creating good things for poor people. Now I want to create good things for myself. Since I stopped being a professional do-gooder I've realized that each solution creates a different set of problems. All you can do is create a daily world that's decent."

"People ask me how I can justify selling cookies with sugar after running a dental program. It's good sugar. It's an imperfect world, but we put the best cookies we can in it." He pushes himself away from the table he's been leaning on, and says, "We're selling good stuff, and I feel good about it."

ANOTHER DUDLEY BUS trundles past, probably late and probably packed, but to make good use of your two bits you take it to the end of the line. Few Harvard students ever will, since the Dudley stops smacks in the middle of Roxbury, but if they did they would find the Silver Slipper Restaurant, "Home of Limbo Patties, Curry Goat and Empanadas," and the nest egg of Leonard and Daphne Matthews. Their tiny eatery is hard to find--with the tracks from the Orange Line blocking much of the light over the sign, and the heavy window grating taking care of the rest--but harder still to avoid, since everyone in Dudley Station seems to know where it is. The place opens every day for breakfast at 5:30 a.m., stays filled with customers until after noon, and finally closes after dinner.

Leonard Matthews works long hours every day, but today he is more aggravated than usual. He's just had to fire new help he'd hired only three days ago, and that means Daphne has to get up earlier than usual to help him with the early shift. "People are so unreliable you can't trust them to do the work," he fumes. "They believe in just turning an egg and that's it."

A slightly brown-skinned man with the hint of a pot belly, he lilts into a delicate Jamaican accent when he stops to talk, especially when favored (West Indian) customers come in. He came to the United States ten years ago working at a ski lodge as a cook ("I used to go to work in true snow storm, man, at 35 below for $1.50 an hour and me from Jamaica? I was ready to go home, man!"). He intended to save enough to start his own business in Jamaica, but he's invested in his restaurant and doesn't now know whether he'll go back home. The Silver Slipper is as much a second start for Leonard Matthews as Grandma's is for Sid Gerstenblatt; but Leonard has weaned his child for eight years instead of eight weeks, and then, Leonard never had much choice about work.

"Since I was 11 years old I worked in restaurants and hotels," he says, "first in Jamaica and then here. I start in an American restaurant as a boilerman, and I watch and I learn until I make it to assistant chef, I don't know anything else."

But he knew he could never make the kind of living he wanted for himself and Daphne working for someone else, "and we wanted to be our own boss," he says, so they borrowed enough to match their savings, bought their store, and taught themselves to keep the accounts. Leonard does all the purchasing and cooking, and Daphne provides the counter service and does the books, and says Leonard, "We do everything together. I make a decision and ask her and if she has a better decision I say okay, we do it. She's a whiz."

Matthews's one and only goal is to be independent, and he would even forsake the security of a franchise restaurant for the autonomy of owning his own place. He was offered the managership of a Pewter Pot restaurant in Central Square, but "I don't want anybody to tell me how to run my place. If I feel like I should sell curry goat or short rib, they going to tell me no. I don't want to be a Pewter Pot." He doesn't want to accept orders from the manager of a chain, and he doesn't want the government to take charge of his business, either. "You work hard-hard and you get your money and you got to invest it, man! It's yours!"

Matthews is also frustrated by his inability to help change his surroundings; he can't, for example, renovate his building because it doesn't belong to him and might get torn down at any moment. More importantly, he hates the deterioration he sees around him in Roxbury.

"I'd like to see our people build Roxbury instead of hanging on the street. I'd like to go into a business where I could take two or three people off the street at least, where I can produce something. But the number one thing to think about is survival. People say they can't do this but they don't try; if I set myself a goal I want to conquer. If I don't, I sick!"

But is he happy? The 14 hours a day, the worry, the gamble?

"Look man." He is impatient, wanting to get back to his customers. "Life is a gamble. Sometimes it pay off, and sometimes things are slow and I take it like a man. Just as long as it's the two of us and we can pay the bills I satisfy. I satisfy."

And back to work he goes.