I've done this for several of my customers. What I did was construct a support for however many gallons I wanted to store. Used horizontal tanks and have done 1,000 gallons so far. Each building is somewhat different. In one case I put the tanks up in the crawlspace and right above a block structural wall, even saving the cost of a support. In most cases the cost of support was always under 1,000. Please understand that to do this comfortably you need to understand load tables for structural beams. It's not rocket science, but just requires a good math background. I'll see if I can find some pictures to post.post some pictures.