Plumbing plus rehab service has quoted $35K end to end to get the job done which is an ENORMOUS cost given my down payment on the home was $55K.

Would I be able buy this property subject-to legally using this method? 

With you and your husbands experience in plumbing I would find a trusted plumber to see what's wrong with the sink and go from there.

Now four years later in the inspection report from my buyer a more dramatic statement is made: "Polyethylene Plumbing Supply Lines have been known to to be randomly defective and can rapture without notice" and the buyer wants me to replace the Polybutylene Pipes in the condo.

Our move in packet has the contact to the tradesmen who worked the plumbing/ heating / electrical on the house.

Where are you all looking for your deals, and/or what methods are you using to get the deals brought to you?? 

My question is: Can the sub 2 method still be used when it has gotten that far?

It will need shower and floor tile replacement, new plumbing fixtures, and the new shower enclosure and going to cost us around $9000 all in.  

But if you're asking how is the value attributable to any land component of a given property acquisition determined, any reasonable method will suffice (e.g., allocating the land value based upon local property tax valuation ratios might be acceptable).

If I want to scale my portfolio, traditional 20% down mortgages aren't going to be possible because of the property value here, so wanted to see what other popular methods are possible.2) How can a rookie investor get comfortable with buying out-of-state?