Invest your money in 3 bbl jacketed stainless steel conical fermenters. If you're willing to double batch some beers you might as well double batch them all...1.5 bbls is not a lot of beer(trying to find 1.5-2bblfermenters will cost as much if not more than a 3bbl...remember economy of scale!!), but you will double your profits.
If your business becomes successful perhaps you could then size up to a 3 bbl system(cutting your time/labor in half)...hey guess what you'll already have full brew length fermenters instead of 1/2... Plus you will have better control over fermentation temperature which is crucial. Ambient cooling/heating might seem to work with 5 gallon home brew batches but in larger scale brewing there will be more volume and heat that will be inconsistently/inefficiently controlled.
There's a lot of ways to cut corners and save money, but its my opinion it shouldn't be done with fermentation/conditioning tanks.
Franklins Restaurant,Brewery & General Store