They will generally get materials from reputable manufacturers like Shaw, Mannington, Armstrong.

@Jon KesslerThe following property types are not subject to these limitations, even if the borrower is personally obligated on a mortgage on the property:commercial real estate,multifamily property consisting of more than four units,ownership in a timeshare,ownership of a vacant lot (residential or commercial), orownership of a manufactured home on a leasehold estate not titled as real property (chattel lien on the home)

Sometimes, they do not even note that building is stick-built as opposed to manufactured housing or a mobile home. 

But until then, she needs a place to live, and since she can't afford to live in her own home, she has to sell it, but because of her low income, nobody wants to take a chance on her)  (I did call a Senior Citizen Manufactured Home Community that understands and will rent a trailer to her based on her paying in advance so thank goodness for someone not being afraid to do so. 

Manufacturer warranties for products like this are irrelevant.

@ Mitch - As far as the inspectors go - they do not care about the manufacture specs - only about building codes and safety issues.

I am currently updating my rental units to the manufactured floating wood floors and/or ceramic. 

The exception to this generalization is manufactured homes located in a land lease community that is owned (at least in part) by the seller of the home.Listen to Bill.

I'm having a bit of a tough time understanding your question, but it may be because I'm having a tough time wrapping my mind around allocating all of the costs to one house.Let's say you are a widget manufacturer.  

It's going to cost to upgrade to the iPhone 5, or any other phone manufacturer.