For a more relaxed pace, I like 600-700 feet vertical rise per mile. Which is about what the Bright Angel Trail in the GCNP is. That would give you a 2-mile path and that is a LOT of path to build.
To climb more rapidly, when I’m in good shape (and you’ll be in good shape if that’s the front walk to your house!), I prefer about 1000 feet per mile. That’s still 1.3 miles of trail.
If there are stretches that require stairs, I’ve built a bunch of long ones and the most cost-effective technique I’ve developed is to take engineered floor joists (TJI’s, etc), paint them, infill the web with another layer of plywood, glued & screwed in place. That makes a very long (up to 48+ feet long, depending on your lumber yard) stringer for a section of staircase. Then I secure 2×8 treads and 2×4 or 2×6 verticals which stiffens the whole thing a lot. A little triangulation with 2×4’s or a section of plywood affixed to the bottom of the stringers stiffens it up even more. Stairs are a quicker way to gain elevation, but 1300 of stairs to too long for almost everyone, so consider some mixed use of them. While stairs can help you gain elevation and maybe span some tricky rocky section, they would preclude the easy, continuous easy of a wheelbarrow, garden cart, or 4-wheeler to bring supplies and weekly groceries in and out of the house.
Suggestion: Volunteer on some trail-building and trail-repair service trips through REI, the Sierra Club, etc. Call your local State Park, USFS, etc and see if they have volunteer opportunities to help work on trails. There’s more to it that it seems at first glance.
And/or hire a former CCC (California Conservation Corps), USFS, NPS trail worker. Whether to help train you to do the work or to build it themselves, they’ve already learned how to and grasp what the job entails.