I know ethically it's not ok to approach homes that are already listed by an Agent, i understand that and respect it.  

I suggest you call and try the front door approach first.  

The contractor and two of his workers were working on the main floor when three men approached and knocked on the front door.

I've actually been digesting the Beginner's guide with great interest, and have a good first draft of my business plan and approach.  

My dad approached me and wants to invest.

You are lucky she is showing her true colors now when you can potentially do something about it as opposed to when she has already moved in.The "I try to help people out" approach to rental real estate rarely works. 

How should I approach this lead with a reasonable offer?

How should I approach this lead with a reasonable offer?

Being a Dave Ramsey ELP, I usually approach these situations from that perspective.

You're spot on with that approach, but determining the outcome (accurately factoring in the profit potential and required time) clearly involves some significant experience - not the kind of thing I should attempt to plan for.