One product when is pretty cheap and also very useful is a laminator.

I bought one back in 2013 and it is still going strong. Basically the laminator makes any sheet of paper you have tear proof and very difficult to destroy.

I use it to help preserve awards my kids get at school or camps, which are often just a piece of paper and usually get ruined really quickly. 
Also I have made signs with it for high traffic areas for the kids to remind them to take their shoes off, lift the seat up in the bathroom and things of that nature. In addition, I use it to preserve my kids art projects.

An inexpensive laminator on Amazon can be found here (for $30):

Swingline GBC Laminator, Inspire, Thermal, 9 inch Max Width, Quick Warm-Up (1701855)

In general you can get a servicable laminator for $30 or less.

Here is an example of a sign I made with the laminator.

The laminator has a ton of uses and is a great thing to have. I go in a little more detail in the following video: