The builder would look at the lot and know.

We had just a minimal slope on our lot and we made it a walk out by raising the house about 3-4 feet. It took a lot of fill (about $9k worth), but the house looks so nice now!!

It will also depend on zoning, as the walk-out basement may be seen as an additional above-grade floor that may not be permitted.

I'll be building a walkout basement almost entirely on grade and be grading

up front and sides up 10'+ high basement from around 100' - 150' away. Admittedly it will take an enormous amount of fill which I have access to however have to hire transport to cart soil from around three miles away.

Check with your building department as well. In my town you need a separate permit and a separate fee if you plan to truck fill on or off site.

I checked but did not see a permit requirement for a fill; for excavation sure. I will despite recheck.