To put a frame around @thatch's last line: general liability for a small interior remodel crew is commonly quoted in the low thousands per year and goes up fast if you touch roofs, structural work, or anything involving heights. Workers comp is priced per $100 of payroll by trade class, and carpentry classes are expensive, so on a real payroll it can be a large number rather than a rounding error. Both vary heavily by state and by your claims history, and a broker who writes construction accounts will give you a straight quote in a week.
The reason investors care is that they'll ask for a certificate of insurance naming them as an additional insured before you set foot on their property, and many lenders funding a rehab require it before releasing a draw. Not having it costs you jobs at the level of client you want.
On the software question, the piece worth building early even without paid tools is a unit-price list of your own: what you charge per square foot of LVP installed, per interior door hung, per bathroom gutted and reset. Two or three jobs of tracked hours and material receipts gives you numbers that are true for your crew rather than numbers off a national cost database. That's what lets you bid a walkthrough in an hour instead of a weekend, and it's the thing that stops you from underpricing yourself into a job you have to finish at a loss.
