Pros:
+ Lowest purchase price, lowest taxes.
+ Virtually maintenance free — no snow shoveling or lawn mowing.
+ Convenient for singles, childless couples and empty nesters.

Cons:
+ Lower resale value, hardest to re-sell and can be difficult to finance with low down payment.
+ Can have large maintenance fees that can substantially increase carrying costs.
+ No private yard so you can't enjoy backyard activities such as barbecuing, gardening, etc.
+ Share common walls with neighbours — if they're noisy you're out of luck.