3. Use clothing as decor. Some of the more special pieces of clothing (the ones that are too small to be worn) still hang on display in my 18 month old's room. It's a nice way to use some of the dresses or tops that you aren't quite ready to let go of yet. This tip doesn't really make the clothing more affordable, but does give you more bang for your buck, which is never a bad thing!
4. Etsy and Ebay aren't bad options. Websites like Etsy and Ebay have a wide range of vintage clothes from tons of different sellers, the trick is finding what works with your budget. Etsy and Ebay both have drop-down options to sort by "lowest price" or "price + shipping: lowest first". It's a good way to see what kind of deals you can find online.
I hope these tips have helped you in your quest for cute kid's vintage! I am constantly shopping for dresses and girly pieces because I have 2 daughters, but these are easily applied to clothing for little guys, too! Happy hunting!