What kind of ammo am I going to find readily and affordable?
Its not hard to find. Usually in the $25 per box range, 180g soft points. Surplus used to be cheap but its all gone now. Recommend stay away from the Pakistani surplus. As mentioned, is best to reload for it. Privi (Serbian) makes a great FMJ round at about $19 a box.
So I should go kill one deer or coyote open-sights and all, then put it back in the safe?
Only if you really don't like them.