Getting free hydroponic materials
One of the great things about simple hydroponic systems is that you don't need to spend a lot to get a lot. In fact some of the most common materials needed can be salvaged from work sites and refuse piles.
General large tubing is used for drainage and sewer lines and are very common at any construction site. Make small talk with a contractor or builder on location and see what they have for scrap drainage pipe and fittings, you be surprised what gets thrown away and how happy contractors can be to have someone take away something that they would consider trash.
5 gallon buckets are also used a lot at a construction site. Granted you should be able to buy these from a hardware store for $5 but free is always better even if you might have to spend some time cleaning drywall mud, or paint from the bucket.
Craigslist and Kijiji are online classified listings and are great for looking for materials for a hydroponic system. If you're thinking about a lettuce raft or DWC system you may want to try an old aquarium that someone is looking to get rid of. Generally people are happy just to have someone take away an aquarium that they just don't want to use anymore. This is also a great opportunity to score a free air pump.
If you are willing to put in the time to search for the items you need you will come across them. But if you don't have the time you can always buy the materials from your local hydroponic or hardware store.