Co-op
You purchase shares in a corporation tied to your apartment. Boards commonly review finances and applications, and subletting or renovation policies may be restrictive.
Condo
You own real property plus an interest in common elements. Condos often allow more flexibility, though building charges and rules still matter.
Brownstone or townhouse
You may control the whole building or own within a converted property. Exterior, systems, insurance, landmark rules, and maintenance require close review.
Choose the obligations, not only the look
The right type depends on finances, privacy, flexibility, renovation plans, maintenance appetite, and intended length of ownership.