On smaller complexes, we have negotiated lower price in exchange for interior access to the apartments. The pm sends flier stating date & time window to allow us access into the units. If tenants aren't there on, say, Tue 8a-12n or Wed 1p-5p, their balcony doesn't get clean. Use rope to pull the gun up, done and done. If the porches are screened, then it is a must obviously to get inside. We have a mid-sized elec unit for that type complex.
If you have 240 units, three story, that is 80 ladder height adjustments and 80 ladder moves (is that right? check my math...). One adjustment for 2nd to 3rd story, and one move for each "block" of three units stacked. Also, 160 trips up & down a wet ladder, not counting swinging your leg over wet railing every time. Unbelievably time-consuming and tiring. I prefer to give up a little revenue in exchange for a lot of productivity. Check with your insurance agent re: interior.