Also with a beach house I think they would be harder to rent when not in the prime summer season where my condo is rented pretty much year round with smaller groups still doing weekend trips.

Beach houses have a very seasonal rental period but Massanutten attracts guests year round.

They really don’t want to pay to maintain 2 places year round.  

Let's round up to $80k. $80k hard cost, $10k lot, $6k soft costs / engineering, etc.

I rounded my interest to 8.67% that is why the difference. 

Kissimmee is a great location to invest due to its ability to attract people all year round.

And I think I rounded up a bit to be safe.  

IF you are going to partner, partner with an experience developer who does not have a conflict of interest.Lastly, if this home were to sell for $1M even, your $120k plus their 800k (lets round down to $900k) - you split $100k profit which is $50k.

Pro Tip: Look for or add language to ensure the property does not get entangled into a "cause/cure/cause/cure" merry go round on the same "cause".

Utilizing a combination of these tools can give you a well-rounded view of the potential costs involved in building a house from scratch.