Honestly, it's too bad that the operating part of your dad's business does not carry with it some residual value of some sort with regards to that commanding a sale price.My hunch would be that this would be far too risky to embark on as a first go of things.Especially, from what you're mentioning this may have a large impact on the quality of your dad's retirement.If you have the funds and can structure something, the place to start would be to engage with an A/E firm to get a cost estimate generated for a concept building like you're mentioning. 

Sound logic. 

The roofers I have used always try to discourage me from doing it, but if your decking is all sound and the existing shingles are still laying pretty flat is there really any downside to it? 

Sounds like you have your ducks in a row. 

Does this sound reasonable or am I crazy for entertaining the idea?

Sounds like a great opportunity. 

It sounds like you are taking the correct first step of educating yourself.I live, work, and invest in the Lehigh Valley. 

Does this sound like a deal or am i just trying to make it into one?

New electric, plumbing, full house sound system, CAT5 and cable lines throughout, original light fixtures and features, new open concept kitchen, master bath, finished carriage house, sports bar in the basement, etc. 

The numbers sounded good.