Should I buy the vacant lot next to a Flip house in MA?

[Steven Tierney]

(I apologize in advance for the long post)

Some background:

I'm interested in a property as a rehab project located in a seaside town here in Massachusetts.  The average lot size as you get closer to the water is greatly reduced compared to the rest of the town, however property values remain high due to the proximity to the ocean.  The current owner of the home only bought the parcel of land which the home sits on, and not the adjacent vacant ( and "undevelopable" as classified by the town due to not meeting zoning requirements) parcel of land that the previous owner also owned in conjunction with the house parcel.  Each parcel is approximately 1/8 of an acre, however, the undevelopable parcel has a significantly lower assessed value due to its classification.  The vacant lot is basically used as if it was part of the lot with the home on it (driveway on vacant lot), but in fact the owners are different, and legally that isn't allowed.   

Here are my questions:

Should I reach out to the owner of the vacant lot (who lives in Florida full time) and see if they'd be interested in selling it (I honestly don't know what purpose it serves for them)? If they are interested, should I buy that vacant parcel, and if/when I get into the rehab property, sell both parcels together on MLS as part of the house rehab deal? Combined both parcels would only be about 1/4 of an acre, but I'd be doubling the lot size in a tight part of town, and could legally market the property on MLS as having a decent size side yard to potential buyers.

If you don't hate me already for the long post, please keep reading:

If the little vacant parcel is assessed by the town at "X" and it serves no purpose as an undevelopable lot to the current out of state owner, what % of X do you think I should offer them for it? Let's say I proceed with this, should I generally consider this part of my rehab costs? How would I adjust my estimated ARV due to the addition of this parcel to the deal? Lastly, let's say I don't get the extra lot... it's always been "used" as if it were part of the house lot... What would you do?? I'm worried the people from Florida might decide to use it one day as a place to park their RV, or go camping or something weird...

You guys are great, Let me know what you think, much appreciated!

And let me know if this should be posted elsewhere on here!