In what way is this sentence ambiguous?

I don't see any ambiguity in it it all.
You want to buy a house in the city.
You do not have the money to purchase a house in the city.

Surely, no one is suggesting that it could imply the person can't afford to buy an entire city?

Ah - perhaps it's ambiguous in that you're not sure whether the person means a specific house that is in the city, or a non-specific house tha

I sense no real ambiguity. The meaning is clear to me.

Anonymous I want to buy a house in the city but I cannot afford it.

This sentence can be ambigous in that it does not clearly state what exactly cannot be afforded:

-The speaker wants to buy a house in the city, but he can't afford that particular house's price.
-The speaker wants to buy a house in the city, but he can't afford

Grammar Geekperhaps it's ambiguous in that you're not sure whether the person means a specific house that is in the city, or a non-specific house that would be in the city once it's found.

I think this is the crux of the matter.

a = 'any' as opposed to a = 'a certain (already identified) one'

Huddleston mentions this example in

I think an American speaker might use the word "this" intsead of "a" if it referred to a specific thing.

There's this girl in my class...
Every day I see this cute dog on my way to school, and today...
I want to buy this house in the city, ...

It is that in-between area of "I know which specific thing/person I am referring to, but you don't, so 'the' isn't right, but 'a'

Grammar GeekIt is that in-between area of "I know which specific thing/person I am referring to, but you don't, so 'the' isn't right, but 'a' is ambiguous."