Assuming there are no other issues like soil, etc that would prevent this type of addition, does anyone have any experience in this, and any ballpark estimates for cost?

If you establish your LLC in Minnesota and put the Colorado property underneath it then your Minnesota LLC will be considered a foreign entity in Colorado. 

You might be sitting on land for a year waiting for permits, soil reports, inspections, etc. etc. before being cleared to build.

I have read much about Radon, and it really doesn't end on just the soil content, as it could also be in the water..

We have zero weather, great soil and everything is “newer”.

You would just ask for a contingency period (aka option/feasibility/due diligence period) that is a timeframe that gives you enough time to find a buyer and hopefully there is enough time left over for the buyer to check what due diligence the seller has in regards to any construction docs (aka architecture), engineering, soils, etc. 

Solar, propane for heater & shower, mini split, fridge that runs off DC, tongue & groove ceiling with puck lights, farm house sink with butcher block counter tops, full bed with storage underneath, 3 seatbelts connected to couch that turns into 2nd full bed, all electric is stored under bench, an induction stove top, fully furnished with pots, pans, and work out essentials, and our favorite part: A ROOFTOP DECK to enjoy the sites.

These factors can affect development costs and desirability.Topography: The land's physical features, such as elevation, soil type, and drainage, can impact construction costs and limit potential uses.Demand: Research the local real estate market to understand the demand for specific land uses in the area.

Does one LLC having all properties rolled up underneath make sense, or would this increase my liability for being sued for ALL the assets under the LLC?  

Sandy Florida soil means you'll get lotsa practice. :)Just as John Kent said, avoid flood insurance by not buying properties in flood zones.