Interested in Language
I think that sentences 1 and 2 are possible. Sentence N3 also sounds ok to me. What about N4, it sounds a bit awkward to me. Is sentence N4 ok to use in speech and is it grammatically correct?
1. How long have you been living here?
2. How long have you lived here?
3. How long have you been selling books?
4. How long have you sold books?
All four are possible.