How should I be thinking about exterior lighting at a 24-unit complex I'm about to take on

Ran a 32-unit 1989 garden style in Gwinnett about four years ago, very similar bones to what you are describing. I went the retrofit kit route on the HPS housings to save money and I paid for it. Eighteen months later three of the kits failed because the housings were already corroding inside, and the color rendering on the cheap kits I bought was so yellow that residents on the parking lot side said it felt worse than before. Full fixture swap to 40W-equivalent LED wall packs, 5000K color temp, roughly 4,000 lumens each, mounted at about 12 feet is what I should have done from the start. At my property that was running about $290 per exterior fixture fully installed, I had 18 of them, and the retrofit false economy still cost me more between callbacks and one liability letter from a resident who slipped in a corner I had underlighted. For the breezeways, vapor-tight strip fixtures only, the humidity in Atlanta summers destroys open fixtures fast and you will be swapping them constantly otherwise. Your $9,000 for 24 units is workable if you get three bids and go direct to an electrical contractor rather than a lighting reseller marking everything up.

On controls, individual photocells on each fixture is the right call at your scale. One dead photocell does not take down the whole lot the way a single timer or centralized controller failure would. I would not do motion-only in the parking areas, constant dusk to dawn on the lot perimeter, full stop. Motion sensing is fine as a supplement in the breezeways to add a burst of brightness when someone is actually moving through, but the base level should never drop to dark. The glare complaint problem from lot-facing units is real and I got two of them. Fixtures with

$9k is workable but not comfortable if the conduit runs are long or the panel needs a new circuit. That's where budgets blow up fast on 1987 builds.

On the retrofit versus swap question, I'd go full fixture swap on the parking lot wall packs, not kits. Kits save maybe $40 a head and then you're fighting driver compatibility issues on 35-year-old housings that weren't designed for LED thermals. Breezeways I'd do dusk-to-dawn constant on at low lumens, around 800 to 1000, because motion sensors in a breezeway create dark gaps between trips and that's a liability conversation you don't want.

The thing I'd want to know before signing off on any of this is whether the current circuits are on a shared meter or individually sub-metered, because if you're pulling from a common area panel that's already loaded, you might need an electrician in before a single fixture goes up.