Arggghhhhh....
The BC&SJ is a moderately large layout with a footprint of not quite 1100 sqft. Mostly it's single deck but there are 3 lower deck staging areas and a lower deck branchline (Redland).
Mainline length as planned will be about 5 HO scale miles (300+ feet), the Deschutes branch (Redland) is about 1 scale mile, the Siskiyou branchine will be about 2/3 scale mile, and the Toledo branch will be about 1/2 scale mile. Non of these distances include staging yards or leads/helix to staging yards.
I started work on the current BC&SJ in Jan 2004 by mounting the Mill City area salvaged from the previous version of the BC&SJ. This area is L shaped with a 12' leg and a 14' leg and gave me the ability to run trains right away.
Benchwork is relatively easy to build (if you have the right tools) and will make you feel as though you're making great progress. Don't be deceived. The vast bulk of the work is in track, wiring, scenery, structures, electronics (control panels), lighting (if the area wasn't lit before you started building benchwork), etc. Progress can start to feel glacial, even when you put lots of time into working on it (after I got laid off in Oct 2008 I sulked and fumed for about 5 months before I became an almost full time scenery builder.
The layout you saw in my "Up the Creek" column in the March 2013 issue of MRH (current issue as of creating this post) is the result of 9 years of working on the layout. I've in sort of working hard mode to get it ready for the 2015 National Convention which is coming to Portland. I don't know how much I'll get done by then but I'd bet it won't be "done".
Right now I'm able to run op sessions again (after a 1.5 year hiatus) which is cool. But it does mean construction tends to focus on that. I built on the layout in a sequence that allowed me to run sessions long before the golden spike was (will be) driven.
Because it's a partially completed layout the mainline is point to point. Point to point sucks for lone wolf operation unless you delight in switching. I used to delight in switching. However the thrill has largely worn off unless the rest of the layout is running. For me, the drive to operate comes from the interactions of multiple trains with mutiple crew (I've had crews of up to 19 people in the train dungeon). A computer program running other trains seems to me to be a poor substitute for a group of like-minded (OK half of us don;t have actively used minds) train nuts scribbling track warrants and trying to deliver freight and passengers to where they ought to be going.
The other thing is, it's way too easy to walk into an 1100 sqft train room and start thinking "Oh Lord, what am I doing here?" instead "Oh wow this is great!" although I do have my "This is gonna be so wonderful when its done moments".
So if you're going to build a large layout,
1. Be sure it can be built a piece at a time so you can do something "useful" with it before it's done.
2. Plan for how long it will take to get the point of seeing something besides plywood and pink foam when you walk in the train room.
3. Be sure the estimated costs (sheets of plywood, feet of track, turnouts, wire, electronics, locos, cars, structures, lighting, masonite, etc) are understood so you don't get part way in and discover you're way over your head financially.
4. If there's ANY chance you'll be moving in the next 15 years, build the layout out of modules instead of built in.
5. Have you seen enough layouts, run on enough layouts, and worked on enough layouts to know what it is you actually want to build/own/operate with a reasonable degree of certainty? If construction is what you like best then this doesn't matter so much because you'll probably be tearing it out (or at least pieces of it) to redo them anyway (ala George Selios and the F&SM). Nothing wrong with that.
6. If the following intimidates you, good! But don't let it stop you from dreaming and building. Just try to make sure you dream and build productively instead of building yourself into a corner.
Good luck in your endeavor, sir!
Charlie