The house is a new construction house built in 2021.

I am now constructing build to rent properties.  

Consider new construction in your state of WI in WI Dells.

As a structural engineer, I could bore you with all the design guides we use for residential or commercial construction, but if you really wanted to get some good sleep, you could look into the Residential Building Code for a deep dive into codes and standards for the construction of homes.

A call to a town building department, or an internet search should answer that for you.2) I have found The Journal of Light Construction to be an excellent source of information.

I understand the lender will determine the value from the construction cost for the lending purpose. 

All cost are from local area Pricing, You could call your local Construction supply company Like White cap or HD Supply.

We then plan to either sell our house and get a VA construction loan on the other lot and build there or if things go really well with the short term rental keep the house and use the cashflow to build another short term rental on the other lot. 

Rest assured; you will always have issues.2) Ask your lender if they are also in the flipping or construction business.

However, I will say that new construction pretty expensive right now, and may be too expensive for the rent income to justify the cost.