Our apartment doesn't have a lot of counter space for cooking, so we decided to build a kitchen unit. We repurposed most of the wood: the 2x4's and top surface from my old woodworking table, the shelves from my old desk. The legs are 4x4's which we bought here in SF and carried home on the bus.
Before we bought and cut the wood, I drew it in Sketchup. The dimensions changed a little, but visualizing it helped us pick our favorite among the design options and think about how it would work.
There were two challenges that made the building process harder than it might have been. First, I don't really have a good surface to saw on anymore. We alternated between the floor of our apartment (for hand sawing, drilling, and hand sanding) and our parking space in back (for power sawing and power sanding). The second problem was, although I designed it with perfect 90 degree joints, I don't have the tools to cut so accurately. (And of course, none of the above-mentioned surfaces are perfectly level.) So some of the angles were a little off, but we made them work.
Altogether, it took 3 weekends to buy the new wood, cut, sand, assemble, stain, and poly. We priced a similar item at a furniture store at around $975. The 4x4s, stain, and finish combined cost less than $50 (and the rest I had already). More than any money saved, though, doing it myself (with a lot of help from Steph) gave it a pride value that beats anything we could have bought at a store.