I was under the impression that the VA loans were only valid if property was your primary residence.

A Real Estate Contract: is a legally-binding document that outlines the agreed upon terms between two or more parties in a real estate transaction and becomes legally binding when signed by all parties.4 Types of Real Estate Contracts:Purchase Agreement ContractsAssignment ContractsLease AgreementsPower of Attorney ContractsContracts Should:Be written in clear language (avoid abbreviations)Include deadlines and specify what happens if not met.List all agreed terms of sale – such as included appliances or home warranty information.Have a written contingency that outlines what will happen after the home inspection.

I don’t think I used any brand specifically but rather ensured that the product had a lifetime warranty.

To summarize... notice to the owner of the foreclosure would be a prerequisite to a valid sale. 

 All architectural shingles have a Lifetime limited (usually) transferable warranty & 15-year 110 mph wind-resistance warranty.

First of all you need to talk to the mortgage lender validating your conclusion with all documentations. 

I'm not sure how valid that concern is and would be interested to hear more individual's experience with that type of setup. 

Plumbing leaks may void warranty.

Most experienced 203k contractors doing 203k work will not allow "self help" because the contractor is liable for all work and materials for the project and must provide a 1 year warranty on labor and materials. 

@Jeff Cagle All the points you bring up are totally valid, but like I said, that model doesn't pretend to illustrate any sort of risk adjusted returns.