If you have a really good production rate of 1000 sq. ft an hour you can do 1.5m sq. feet in only 1,500 hours wand to the carpet. That is cleaning hours only and not likely doing HWE with a standard wand to get that type of production. Not set up, move, refil, pre vac, moving furniture. If you put in 40 hours a week, at this location, it would take you 37.5 weeks to complete....just wand to carpet. no breaks, no down time. 37.5 weeks straight cleaning.
How many trucks can you run there at once? Is this night work?
Basically if you take this job, it's all you'll be doing for a year. I wouldn't do it for less than .10 sq. ft (and that is pushing it, likely closer to .15) and that is working regular business hours. Night work would be more. That being said .10 would be $150,000. Can you make more than $150,000 a year servicing your other clients? If you take this on an then can't service your clients, what happens if you loose the contract? What would be your labor and materials cost to take this on. How much profit would you see from that $150,000 if you priced it at .10?
So much to consider.