What are some non-adobe alternatives to photoshop that don't charge monthly?

Greed is a funny thing. 

Well, I for one am not going to pay $50 a month to have access to photoshop and premiere when I BARELY ever use them.  I'm not a professional editor, I just like to use the programs when I DO have something to edit.  There is no good reason why I or anyone else like me (or anyone else in general, EVER) should have to pay several hundred dollars EVERY YEAR to use a program less than twice a month.  SO, does anyone have an alternative to photoshop?  I've already downloaded iMovie (for FREE I might add) but not sure what to replace photoshop with.  Thx!