Your going to buck down your power from 480/3ph to a 208/110 single phase..220/240v is not really a commercial voltage used in warehouses..480/277v on the high leg and 208/110 on the low leg, pretty much the same everywhere with few exceptions. You do need to know how many total amps you have to work with though. Your going to have to pull permits and have all the work done by a licensed electrician to have any chance at all passing local inspections. You can run 480v ballast with any ceiling shorter than 12 feet and pass NEC code inspections. Your going to easily spend $10k on electrical alone, a 400amp 208v distribution panel is $2k with out breakers or installation, then you have to run all you circuits tho the rooms.
Do not use OSB for anything in a grow, ever...It is a high temp, high moisture environment OSB will absolutely not stand up to the conditions even short term, plus will not pass inspections. I would treat all wood studs or use pressure treated sills at least unless you can knock out a steel stud frame which is preferred.
5 tons for every 12-15 DE fixtures,
Nanolux fixtures will cost you around $350 per unit and pull about 4.8 amps at 1000w
I would hang Uni-struts from the ceiling on 5' centers and hand your fixtures on those. I would run the walls up to the roof and not try and put a ceiling on the space because that ends up being a huge expense and is not required. Much easier and cheaper to run lighting circuits and HVAC without a ceiling over your space. Plus, I see the roof is insulated so your half way there already.
Realistically your looking at around $250k to build out 3500 sq.ft. and do it right but you can do it for about $1000 a light all in or approx $1000 per 32 sq.ft. of lighted surface area
