If you are buying to live in, any time is right. If you are buying for an investment, it doesn't matter if it is the bottom or top, you have to pay attention to each property you are looking at. Just because it is a foreclosed property that has been marked down 50%, it may not be worth it. On the other hand a waterfront home may be worth a full price offer.
My rule of thumb is to establish the value of the lot and subtract that from the price. Divide that price by the square footage of the home and compare that to the current cost of construction. If your home falls in the 65% of new, you are close to the wholesale price.
Remember, it is the land or location that appreciates. All houses depreciate with age. The trick is to find the right location that apprciates fast than the house depreciates.
I follow Miami property, it is still falling. high rises and condos along Brickel are selling for nothing, but would you want to live in a 30 story condo with a few families? consider the risk in maintenance, HOA fees (yeah there will be some), vandalism, squatters, crime, etc. etc. yeah living along Brickel is nice (although gets very fast into very bad neighborhoods) but what the cost?
lots of short sales, and foreclosures. a lot of foreclosures are going 'as is', and don't have fixtures, light or otherwise. homeowners are gutting the houses and causing major damage so that has to be double checked. whatever you do make sure you hire a structural engineer at the very least.