If you need a bunch of pots or just have a large area of ground to fill with rich soil... the cost can add up very quickly. Let's explore some ways to get what you need for cheap!
Be creative! Check garage sales and thrift stores for not only regular planters, but anything that can be used as a planter! Just make sure you can drill holes on the bottom of the container for better drainage. If you don't care about the way the planter looks you can even use jars, jugs, and just about anything else laying around the house! Just keep in mind, plastic or metal containers will not "breathe" as well as pottery or wood, and some plants will need a decent sized pot to grow in.
Build one! There's so many unusual designs out there and many can be made for cheap with a little bit of wood, plastic, fabric, etc. Here's a great modern design, and this one is easy and cheap to make! If you don't have much space to work with, building one may be the way to go so that you get exactly the right fit for your place!
Don't forget, regular planters can also be picked up for cheap at dollar and discount stores.
As I mentioned in my last gardening post, check Craigslist for free soil if you need a lot of it and have a way to haul it. The only problem is that a. you have to dig/haul it, and b. it can be messy unless you have a truck you can just hose down. The other problem is that the soil might not be that rich depending on where you get it. Still, an option to keep in mind.
If you only need a little bit of dirt, check the dollar store. Some of the nicer dollar stores in my area will carry small bags during Spring and Summer.
Last option for cheap, rich soil is to make your own if you can! You will still need some regular dirt, but starting your own compost pile is easy! You can also get cheap compost bins to keep inside your house for scraps. Here's more information on composting!
If you get serious and want a chunk of land to work on, do a search to see if there is a local community garden nearby. Not only do I have all the plants to maintain at my house, but now I have a big lot at a garden run by the city as well. Rates vary, but I know for my garden it costs about $300 a year. Some of the gardeners are so into it they have 3-5 plots and pretty much live off their produce, which is a great idea for vegetarians and vegans! I've also heard of people swapping use of their land for fruits and veggies. Check Craigslist and forums for ads, or create one for yourself if that sounds like something you would like to do. Both parties benefit! If you're really adventurous you could possibly create your own community garden for a group of you!
The last idea is a little risky and you may not be able to reap the rewards, but have you heard of guerrilla gardening? The idea is to "bomb" an area with seeds or plants - whether it's a vacant lot, or a sidewalk planter that's looking kind of sad and lonely. I think it's a neat idea, providing the owner of the space doesn't get angry about it. Why not share some pretty nature love with the rest of your neighborhood or city? Check Etsy for cute homemade seed bombs and keep your eyes open for uncherished ground that's begging for attention!