I can't imagine a Harley would be in that price range... and if it is, it's probaly NOT something you'd want as a dependable back-up.
Nothing wrong with the 750 Nighthawks if you just want a dependable commuter. They've earned a low-maintenance reputation. A bit boring though. If you can find a good clean one, a Nighthawk 700S from the 80's would be more fun, just as reliable (same basic motor with a shorter stroke due to the Harley Tariff on imports >700cc in the 80's), plus the 700S has shaft drive instead of the newer 750 version's chain. (The 700S was a 750S everywhere else in the world except the USA.)
OTOH, for the $2-3K price range, you should be able to pick up an older B6 or B12 and they're reliable and since you already have a newer B12, be very familiar.