Hm... 18-20 months... you might be behind schedule. ;)
Serious suggestion, though, having gone through this process recently: Have you considered a manufactured home? They're a whole lot quicker - ours went from "signing the paperwork" to "installed" in about 4 months, and a bunch of that was waiting on the foundation folks to get time to pour the concrete.
We've got a 2k sq ft double wide, and it's easily as well built as a stickbuilt home - I did a factory tour and came away very impressed (I've done enough construction work over the years to have a faint idea as to what I'm looking at). Other than the floor plan being "obviously manufactured home," you really can't tell from the inside.
With 2 acres, you can go with a single story home and avoid stairs, which we thought was nice. More roof area for rainwater collection and solar as well.
All I can say with the permit process is, "Start early." It'll take longer than you think, and you'll learn more weird things about permitting than you ever wanted to know.