An EOS IV HS still sells for around $1000 or more in these parts. I'm not sure everyone here realizes how much the HS part of the camera is worth!
Used M2s go for $500-800 depending on the condition. Forget the M2 trade and wait until you get a good offer on the Canon (maybe even use it while you're waiting), then you will have enough money for a used M2/M3 and some CV glass, or just more money for glass.
And don't let your girlfriend tell you what to do! As long as I keep paying my share of our expenses my girlfriend has absolutely no business in how I spend my earnings! 😉