Not a bad idle game! As has been mentioned already, the Tax aspect does seem to against the idea of the game, forcing you to keep checking the game rather than letting it run on idle. If you're lucky you'll check at the right intervals and pay your taxes; if not it'll cost extra... but it's a good thing the cupcake industry is funded by cupcakes rather than money, at least, so you can progress regardless of how well you do with tax.
The test drive feature feels a bit limited with only the parking area, but it's a fun idea, and nice how the property you buy/car you drive is shown on the main screen too, gets a bit more personal that way. What would be cool is having a visual 'Cupcake Industry' in the background, that keeps growing as you keep expanding your business. And how about putting a cap on how high you can go, when there's no highscore or similar to reward progress further than the medals? Feels a little pointless with a game that can go on forever... even an idle one. (At least I assume it can go on forever?).
Well, all that said, the upgrade mechanism works well; the interface feels intuitive too. Graphics aren't the flashiest, but they do the job! Fun little time-waster, simple to play, with some entertaining tid-bits of story on the side (though they easily pass by unnoticed considering the genre of the game :). Hoping; looking forward to a third installment in the series! Nice work.
-cd-