As all of the SD cards I have right now are used for my cameras.
Also I am only 13 - I can't really afford to buy SD cards. I know that might sound stupid, but to get a class 10 SDHC card with a reasonable amount of storage, that can cost £15+ who only gets £5 from a paperround a week, it can be quite expensive.
I fully understand. However you only really need something like a 4Gb Class4 SDHC or micro-SDHC card + adapter to start with, especially if you already happen to have a spare USB flash drive about. You should be able to find 4Gb ones from, for example, amazon or an amazon store for around £5 or less if you're lucky. Many of mine are Kingston brand and I've had no problems with them.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, A+ and a B2) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm