I've done this the last 2 winters, bought a red sweet pepper at the grocery store and saved some of the seeds for planting that spring.
There are actually a few fruits and vegetables you can grow from produce purchases. I began my garlic with grocery store garlic, planting all the cloves from one head and multiplying over the years. I've planted sprouted potatoes, harvesting many times over what I planted. I've grown green onions in a cup of water on the windowsill from the leftover root end of purchased green onions. I've heard you can regrow Romaine lettuce and celery from their bases. Pumpkin, winter squash, and tomato seeds can be dried and saved to replant. And of course, there's always the avocado pit suspended with toothpicks partway in a bowl of water. My mother grew an avocado plant/tree for several years. It never grew large enough to be a tree. I knew someone who grew a pineapple plant from the crown of a fresh pineapple. She lived on Kauai and had the right climate to actually grow new pineapples on her pineapple plant grown from a crown.
With some of these plants, the variety you harvest might not look like the parent from which you took the seeds. I've found this to be true of winter squash seeds from market squash. Most of the peppers I grow from scavenged red pepper seeds are green or yellow at the time of my harvest. But I'm satisfied with the green or yellow ones.
Growing a garden dirt cheap is possible if you have a sunny spot in your yard and you're not terribly choosy about what you grow. Seeds and plant starts can be free -- remnants reclaimed from your trash or compost bucket.
Anyway, we've enjoyed our purchased red pepper for the winter months and now I've set aside my sweet pepper seeds for this summer's garden.
