Data Center Relocation

I have been tasked with working out a rough estimate on relocating our existing Data Center. The problems are that they can't provide me with a location that we might move to, they are giving me a list of possible locations. I am sure that my most affordable would be a move inside the building, but I am still trying to figure out the best way to estimate this. Our current Data Center is a remnant of when there were mainframes in operation here. We could probably downsize to approximately 1/4 the floor space we currently have. I just want to get some recommendations as to how to best go about this.

Thanks