This is a question for you pros out there. I have an opportunity to bid on a job to tile kitchen floors at a 275 unit apartment complex provided the price per unit is cheap enough. The existing flooring is full glued vinyl ( non cushioned ) over plywood subflooring. I spoke with someone @ Home Depot and was told that 1/4" hardiboard laid in mortar bed and screwed to subfloor would be sufficient without removing the vinyl flooring. Here are my questions.
1. What type of prep needs to be done to the vinyl prior to applying mortar?
2. What is proper treatment of seams created between sheets of hardiboard?
3. What can I expect to be able to charge per square foot for labor in this situation for say 20 units and for entire complex?

Thanks in advance for any assistance.