That is not a very easy question, a basic starter house can be from $75/ft to $125/ft.
We stopped doing new build spec homes about a year ago, they can be profitable, but they can also take a long time to sell. Research your market.
You need the plans, selections, location for planning and permits and a good schedule.
What is your sub base relationship, do they work together and can you have more than one trade working at a time to overlap them.
Time will kill your profits because of holding costs ($100/day), you need to plan and schedule each trade with no lag time.
Get solid bids from each sub, completion fair date with chargebacks if they go over on their time.
We were using Buildertrend software now we just use a simple house flipping software spreadsheet for both.
https://getdpd.com/cart/hoplink/17288?referrer=1htchomtp7lwoc
Hope this helps, Make a schedule and an Itemized list for EVERYTHING
