You can try Stencyl, that is also free. Visit Kongregate for tutorials.
Flash is not that costly, it only makes itself out to be that way. Though, if you want to monetize your games, you probably should buy the full version. You could learn with the student-educator version, then when you are ready, you could buy the full version.
The full version of Flash is US $699.
The student-educator version is less than a third of that price, at US $199.
Oh yeah, and if you still want Flash, you could get Flash for neither $699 or $199, heh heh. (And no, I'm not helping you if you choose this option. Truth be told, you might want to give this option a miss. Especially if you don't want to be pulled out of your house feet first and put in a 6 by 4 foot room with barred windows.)