The problem is that I have only my sister to help me buy fish supplies, and $25 is more than she's willing to pay. Upon further research, I found three different test kits, one for ammonia--the one I showed you--one for nitrite, and one for pH. Altogether it's about $20, so not a lot less, so either way it's more than she can help me pay for right now.
Either way, I'm most likely going to have to spend all week working for some more money before I pay my sister the money I owe her for the filter, and then get the test kit(s). I'm okay with this--I like working and staying busy. I just hope I can find enough to do to earn money soon!
Again, thanks for the help! I didn't even notice at first that the test kit I found only tests for ammonia!