Going by sq ft is a pain for houses. Just set yourself flat rate for a couple of different categories of houses
1 story 1,000-1,800 sq ft
1 story 1,800< sq ft
1 story with walkout
same goes for 2 story…
take off 25% let them know that you are doing that though, to show them the quality of work you do in hopes of creating a business relationship. Instead of just giving them a cheap price and setting their expectations for future work.
Sometimes giving away $50 is worth the $10,000 it could bring in.