I individually priced all my materials and got several estimates from contractors.

Materials have increased more than 20% in the last 5-8 years.

What is the best way that you have found to tell them that you need labor & materials separate, so at tax time you can send them a 1099 for labor?

ACM (Asbestos Containing Material) abatement is a tough one because often you won't know (outside pipe insulation & 8x8 tiles which I can spot and point out with no testing).

A good baseline is to calculate material costs (e.g., $300 for paint and supplies) and add a fair hourly rate for labor.

I have spreadsheets filled with material lists for every phase of the build that includes pricing for materials as well as labor, and sources that I use for them.

With labor and material, and not counting the identification and obtaining the addresses of owners and matched to properties, I guess about $2.00 per letter. 

Scrren PMC's by asking if you will get the material invoices AND the actual invoices from any contractors they hire. - Be prepared to pay for a PMC's time!

At the end of the project's life the land must be restored to a natural state and the materials must be recycled if possible, eg. stripping out metal, etc. 

If you're still interested, take a trip to the site once ground has been broken.The flashy marketing material for a new development is great, but don't put your money at risk for something that's likely to vaporize.