Boris' response is a perfect example of why co-ops get shafted in markets like DC that don't have a lot of them - even the realtors don't actually know the myths from the facts!
Maybe this will help:
Myth: co-ops always have much higher fees than condos.
Fact: only a few of the old, luxury co-ops (e.g., the Watergate) have really high fees. The rest are about the same as condos (around $500/mo), and, unlike condos, co-op owners have total control over fee increases. Fees only appear high because they include property taxes, the "underlying mortgage" (see below) and often some or all ulitities. And when you account for tax and other savings, total non-mortgage expenses for a co-op unitl are often much lower than a similar condo.
Myth: You have to put 20% down on a co-op and only few "approved" lenders will finance them.
Fact: Many lenders finance co-ops and permit 10% down or even less (we did 5%), and rates are very competitive. Moreover, the "underlying mortgage" (i.e., the mortgage on the co-op building itseld) is subtracted from the sales price, so a buyer has to finance a smaller total amount (meaning less $$ down and potentially avoiding "jumbo" rates). So if a unit sells for 700k and has an underlying mortgage of 100k, the buyer only has to finance 600k. The other 100k is already set and paid monthly with the HOA fees.
HUGE Myth: Condos offer tax benefits over co-ops.
Fact: Tax deductibility on a mortgage co-op - including the underlying morthahe - is identical to that of a condo. More importantly, property taxes on a co-op unit are a fraction of a condo. For example, DC taxes on a 1500 sq ft co-op will run you about $1300/yr, while taxes on a similar condo in the same neighborhood will be $4k-$5k! So you save thousands per year.
Hope this helps. Yes, co-ops have rental restrictions (although not nearly as restrictive as people think - you can still rent, just not infinitely and/or to any shlub off the street), so they're wrong for people looking to buy a rental property but great for people who are looking for a home and don't want be surrounded by an endless stream of noisy/messy renters. And they're always priced at a significant $/sqft discount to condos. So if you're looking for a great deal on a HOME, do yourself a favor and get to know the facts.