I agree , its is involved, I did a job , 3 years ago 500 flats , some partially constructed, took 65 men, 15 weeks to clean and cost 800k , pity it i was only managing it for a larger company was good experience though, 8 steam cleaners jetting a massive underground carpark , 14 lift shafts, all common areas, loads of voids and false ceilings. My advice is to get raining , or get some one in to project manage it for you .