Well, I paid about 250k for a 100ft by 100ft concrete floored hangar with toilet & shower (the septic tank cost 15k!)
Work out how many aircraft you can fit in that to give an income of about £25k a year (gross) and then deduct hangar keeper's insurance, electricty, water bills, maintenance (even just gutter cleaning!) and something for depreciation!
In my case, I am over 50 and the hangar is meant to have a 40 year life - so I am not too worried about depreciation!