$310 is a stabilized-year number in a market with slack labor, and neither condition is likely in a flagship market during the August turn. Purpose-built operators at your size typically carry a per-bed turn number that covers paint, carpet or LVP repair, cleaning, keys and lock cores, and the make-ready punch on the shared spaces, which are the parts a per-bed figure tends to leave out. The shared kitchen, living room and hallways in 24 units get consumed by four people each and don't appear in a per-bed line at all unless the seller allocated them. Ask for the actual invoices for two consecutive August turns rather than the T12 line, and separate materials from labor, because labor is what spikes when 40 beds and every competitor's beds move the same week.
On concessions at zero: that tells you the last leasing season cleared without them, and nothing about the next one. In student markets concessions show up late, in June and July, when the remaining beds are the leftover ones in four-bed units with three signed roommates. Those are the hardest beds in the building to place. Model something for the tail of the season even if it wasn't needed before.
Rent-only guarantees mean your bad debt exposure on unpaid rent is genuinely lower, and your damage recovery runs entirely through deposits. On the third of beds with no guarantor and a higher deposit instead, run the deposit against a realistic worst case, one skip plus damage, and see if it covers. It usually doesn't. Whether you can even apply a deposit that way depends on your state's deposit statutes and the notice and accounting timelines they impose, so have counsel in that state read the form.
The thing I'd chase harder than any of this is the university's own housing pipeline and any live-on requirement changes. A flagship growing 1.5% a year that adds 800 beds of its own can flatten your absorption in a single season, and that decision gets announced years before it lands. Enrollment growth at the institution is doing the work in your rent assumption, and campus supply is the variable that can break it while enrollment still looks fine.