Added the legs to the basic frame today. I went with a very cheap set of tools, and at least where the screwdriver is concerned, it was not worth it as the head has stripped after only a couple dozen screws. Below you can see my hand saw and drill; the drill is fine, but it's impossible to make any kind of straight cut with the hand saw, at least not without some kind of cutting jig.
The legs are bolted on, and it took me a couple tries to figure out how to line up the holes correctly but I finally happened on a method that worked perfectly. I will add some cross braces to the legs, as well as a temporary shelf for storage below that will sit on the cross braces.
The yard extension is assembled but not yet bolted on. I think I will need some support for it since the bolts will not be enough to hold it securely to the rest of the layout. For now the framework is serving as a worktable and storage space for my Dreadfleet set!