I'm trying to get the final kitchen upgrade for one of my families. They've got more than enough $$$, but I keep getting a message saying the upgrade is unavailable. Wassup?

This may seem like an obvious first question, but have you already purchased the second upgrade?
I can see the appeal in waiting until you have enough for both and going straight to the third, because that's what I did with the... workshop, I believe.

That's exactly what the difficulty is. The exact wording is, "This upgrade is not available yet!" The key word there is 'yet,' since the Level 2 upgrade must be purchased first.

How could I have been so dense??? I never even thought to check if I'd purchased Level 2. Thanks you guys!

Don't feel bad! I did the same thing in one of my games, and couldn't work out what was wrong for several minutes. I closed the game, reopened it, still the same message. It was the third game and I'd already got L2/L3 in the others, so never thought to check.