A random photo of the boys doing lesson work a few years ago.
People can and do homeschool for very little money. I know one mom who made such extensive use of her public library that she spent under $50 annually for workbooks and other resources.
Libraries truly are one of a homeschooler's best resources (public television is another). I used to plan blocks and place hold requests for all of the books I needed, and since they weren't in high demand I was always able to keep them for the six weeks or so that I needed them. Wandering around my library one day I found a whole section of books to teach mathematics which allowed me to "test" a few programs out. I also used books from the children's section that introduced many math concepts. There are so many fantastic non-fiction books (and fantastic fiction books too, of course) available, in subjects ranging from grammar to history to science.
I think the hardest resource to get from the library for use during the entire homeschool year is a math curriculum, and indeed, having used many programs over the years I have come to think that the most frugal math resource is the one that you will use and that your children will learn from. We did really well with Waldorf style math blocks in the early years, and then later with Oak Meadow math for 7th and 8th grades and now with Teaching Textbooks. I truly think TT is worth every penny spent on it!
Many districts provide curricula for free, and there are charter schools which provide funds to buy materials as well. Homeschool groups may have a lending library of curricula and other resources.
One way I have saved with homeschooling is to sell everything after we have used it; indeed, I usually bought used curriculum and then sold it for not much less than I originally paid.
A lot of homeschoolers go on field trips very often, which is fun but rarely frugal. We went on fewer field trips, focusing on those that were free or very low cost, as well as those that were close to home (so we could spend less on gas and also be home for meal times). This allowed us to splurge every now and then (not even every year) on a bigger experience, such as spending a day aboard a tall ship.
I never found that my boys learned a lot from most field trips anyway, at least not when they were younger. Many kids tended to see it as a time to socialize, so even if my boys were trying to pay attention there were often other kids who were being disruptive. (Not that my kids are perfect - i recall all too vividly a field trip last year where my two kept talking to a friend and I ended up separating all three of them.) Instead, we incorporate many field trip type activities into our own travels. On beach vacations (wonderfully educational in and of themselves) we seek out nature centers, tide pools, and estuaries. In cities we look for museums with exhibitions that will appeal to the boys.
I encourage home learners to find things that are free or cheap and educational in their own cities. Our town has a small postal museum that my boys learned a lot from, and we could stop in whenever we were at the main post office. We also have a summer concert series each year, as well as a Shakespeare festival. Local bookstores hold various events, and other area stores offer free crafts.
Being in nature is one of the best ways for young children to learn, so finding local trails is worthwhile. I like to take the same hike once each season so that the kids can see how it changes throughout the year. One year we went to a local nature park every week to observe seasonal changes, which was really neat.
Of course, being in the home is a wonderful learning experience as well. There is so much to learn from cooking together, raising a garden, caring for pets, tending the home. making music, and more, and yes, many of these things translate into traditional learning subjects. Many schools themselves now have gardens, and my mother-in-law often did cooking experiments with her students.
Let me not forget grandparents! Visiting grandparents in their home towns gave us more places to explore. One year my in-laws watched the boys for several days and I asked that they take them to the local mission on a 'field trip". They did that and also planned nature walks and a visit to the landfill.
Our recreation center offered low-priced sports programs; we would pay around $40 for three months of basketball, and received a discount for the second child.
I hear from so many people how expensive homeschooling is, and based on everything I have written here, I have to say I disagree!