Pros and Cons for this accommodation. The pros are: pleasant non-intrusive hosts, close to Columbia campus, secure building with elevator, safe neighbourhood, fair sized room with fridge, TV and air conditioner. Apartment is at back of building and away from street noise.
Cons are: old building with old plumbing and frightening wiring! Bed is most uncomfortable - it's a flattened sofa bed topped by a thin mattress which does not disguise the ridge running down the middle. The air con is poorly fitted allowing drafts directly onto the bed. The only table is a computer station and only seating a wheeled typist chair. Not a kitchen to cook in - although I had free access to kettle and microwave. Subway and shops are on Broadway - a 7 minute walk through Columbia campus. It's a fair traipse back if you forget something.
This place is best for students or relatives visiting students for a few days. Those looking for a base to sight see NY for more than a few days would probably be better off paying a little more and getting accommodation nearer downtown - with a proper bed!

Tip: The best shops on Broadway start around 113th Street - so walk down a little. And if you get a chance, check out Riverside Church opposite Grant's Memorial - it's amazing and not well known.