Closed cell spray foam

Hi guys,

We're a contractor looking to do (requirement from city) closed cell spray foam in the attic roof rafter spaces. We need an r15.

With 1800sq to do im thinking large barrels and sprayer to get at least 2" for the whole roof purchased from a wholesaler.

Ive seen the $400 kit at depot but wouldnt cover the area needed unless we bought 8 kits.

Would it be better just to sub it out? Or worth it to buy the tools ourselves and do the work.

Any other ideas or thoughts please let me know. This is in the hills of southern california.

Thanks,