I am also building a spec home, actually should be breaking ground next week, fingers crossed!
IMO, the deal looks way too skinny for me. You can EASILY go over budget by more than 10%, there are LIKELY going to be delays increasing holding costs, etc.
I am not a tax expert but here in AZ unless you hold the property for more than one year after completion you are subject to ordinary income tax.
Unless you are in a very low tax bracket, capital gains tax would be less than ordinary income tax.
I am 99.9% certain that the 5 year period to avoid capital gains starts once you declare the home your primary residence, that is, once you move in.
Honestly, the difference between ordinary income and capital gains, dollar wise, isn't that much on 130k. I would definitely re-evaluate your numbers. In my case, I expect to invest about 800k ALL IN and expect a 1.25-1.35M sales price. I think my deal is even a little thin but I enjoy the process and every project is a learning experience.