It all depends on the material that was installed on the roof. 

I had to rent a storage unit for my tools and materials to do repairs, and I had to pay someone to use their shop to actually work on things (for my business: repairs, maintainance things. etc...)

Approval took a while: first - the Plans Examiner sent them back, requiring that we specify fire rating of materials because they want to ensure a fire in one unit will still allow the occupant of the second unit enough time to escape the property.

In California we Pre-Lien every time we start a project.We always inform the home owners that is not a Lien or even a attempted to Lien, but that its only to follow the letter of the law and be able to protect all parties involved which in most cases includes the Material Vendors.You'll be fine.Live and Learn.Cheers

Layout and materials are the same as what was there before.

Why are they letting tenants handwrite modifications to material terms?

He needs to have connections with other trades in the area, vendors, etc.Last piece of advice, make this person get all supplies, materials in his or her name, not yours.  

You could even review the material in the AdWords certification program (all free now).

The source of the water is external and can be remedied with a sump pumb/perimeter drainage inside as well as a dry well outside.

Easy to repair or replace, don't make it too nice or you'll be paying high dollar all over again after tenants trash stuff, use rugged materials.