Radcliffeborough is a great neighborhood in Charleston! It would be a good choice for your home.
If the property that you are considering is currently a duplex, it likely that the home is not zoned for single family use. That being said, dingle family zoning would be a downzoning and there are other single family homes in the neighborhood so I would think that you could get the approvals that you need. You or your representative should contact the City of Charleston Planning Department for guidance on the best way to proceed. They will need the Tax Map Number to identify the property. If it is a legal duplex, it should have two tax map numbers. I chair the Mount Pleasant Planning Commission and we normally don't have any issues with downzoning unless adjacent property owners for some reason take issue with the change.
I hope that this was helpful to you. Please feel free to contact me if you need additional information.
Keller Williams Realty