A yo-yo only captures a child's attention for a short amount of time. Unless he learns advanced tricks, he'll tire of the up-and-down toy in a couple days. If you think your child will only play with a yo-yo for the short-term, make your own instead of buying it. You'll get more enjoyment out of the yo-yo by taking the time to craft your own and you'll keep the cost down by using items you already have in your home.
Place the buttons back-to-back with the smooth sides touching. Sew regular thread through the buttons and tie them together with a knot.
Measure a piece of cotton thread long enough to reach from the floor to your belly button. Add 3 more inches and cut the cotton thread from the spool.
Wrap one end of the cotton thread between the buttons twice and tie a knot. Position the knot as close to the center of the buttons as possible. Trim off the extra tail.
Tie a slip knot in the opposite end of the cotton thread. Fold the thread through the slip knot loop and stick your finger through the new loop. Wind the thread around the center of the buttons. Play with your homemade yo-yo.