Bryan,
We were in a similar situation in 2009-2010 when we bought our dream house. Well, it better be, because we have moved 13 times, are retired, and do not look forward to yet another house or move.
The new house basement was unfinished (one of the conditions to buy the 1-1/2 year old house), was large (about 2300 Sq Ft) and had nine-foot ceilings. After much consideration, I divided the basement to allow for a nice workshop, study, exercise room, full bathroom, and utility room. This left a 33 x 38 space for the train room.
I had a year to work on the track plan from the moment we bought the house in 2009 until we moved in 2010 after selling our then current home. We were fortunate in being able to rent the new house to a couple we knew, so the house never was empty.
The track plan I settled on, after close to 30 iterations plus sub-iterations, has been great to run trains and to show them to our many guests, which number at least 297 to date. I made a change early on, before I started laying track but after I had finished the bench work in that area, and that was to add the Millhouse River 34” turntable. I also added a short spur, but that was very easy to do.
We moved in August 2010 and I was able to finish the entire basement by January 2011 doing all the work myself and while I was still working full time. In February 2011 I started on the layout, and had all the track, main wiring, and some scenery complete in about a year. The layout was 90% complete about a year later, and I have continued to add a few details now and then.
I couldn’t be happier with my layout.
Good luck and don't hesitate to contact me if you have any questions.
Alex