Mario said there's "junk trash, from furniture to construction material.

A builders risk policy removes these exclusions and can add coverage applicable to the rehab, like coverage for materials on site, etc.disclosure - I am familiar with all of the products as I was a State Farm agent many years ago, and rep for all of the companies mentioned above.

What materials make sense?

In addition current opinions as of the date appearing in this material only and are subject to change without notice. 

It is also possible that a contractor may purchase it because s/he would have the skills that decreases the labor and materials cost for this kind of project.

She gives you reference sheets with pricing that is super low (not accurate) for building materials to use when calculating rehab costs. 

To what quality of materials.

Not only for the value losses, but also for services EquityBuild paid to the General Contractor for construction and/or materials, which subsequently resulted in numerous Mechanic's Liens against the properties from the General Contractor failing to forward and pay those funds to many of the sub-contractors and suppliers performing the work.

Your loan balance may end up way higher than your purchase price, all those labor/material costs were rolled into the loan... which you can of course pay off asap with no prepayment penalty. 

2: Check out the Learning Materials - you'll find everything you could ever want for pre-purchase due diligence, general rules of thumb etc.3: You don't trust your uncle?