Any fitness people have some simple exercises I could do?

I'm just asking for the hell of it. I'm 5'8" 300lbs. For now I'm doing 3 mile walk(about half a mile is up hill), 50 pushups, 50 situps, and calf raises daily. If anyone says walking isn't enough I'm gonna curb stop them.
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I suppose I'll note the reason I say if you say walking isn't good enough because if I run/jog it's ineffective for me. I can only do it maybe a half a block max and it destroys my legs so I can't stand going for even a walk for like 3 or 4 days. I actually can't even stand walking around my house after jogging. I figure once my legs are stronger and I lose some weight I can step it up to at least have part of it be a a jog.
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+1 y
Oh and last. I'm broke. My suggestions have to be pretty much free. Also making healthy food for the most part a problem. A lot of healthier food tends to be expensive. Especially fruits. Which sucks.
Any fitness people have some simple exercises I could do?
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