No. It's an issue for the post office. The post office doesn't talk to the
city planning commission and is indifferent to local zoning laws, occupancy
requirements, and other infringements on the use of your property.

Try it out. Put up a mail box with the address of "1234 1/2" on the box and
mail yourself a letter.

Even if true (and that I don't really know for sure is USPS policy) that
doesn't make it "legal" nor conforming to local zoning which depending
on jurisdiction may be enforceable usage of the property.

I'd certainly advise OP to not invest in a property on the assumption of
usage at variance w/ local code and zoning at the risk of a sizable
economic loss.

The key person to talk to is your postmaster in the local post office
serving your address.

When the mail is sorted for a carrier route, typically there is an
official pigeonhole for each unit at the carrier's workstation where
they sort the mail. Each pigeonhole has an "official address"
associated with it. The USPS determines what exactly that address is.

You can see your official address if you go to: http://www.usps.gov

and do a zip code lookup of your property. You might be surprised at
how the post office wants it to appear versus what you have been
using.

Your postmaster will tell you exactly what you need to do and if a new
address can be created. There may also be issues about mailbox
placement and such. You have to follow the USPS rules....

Also, sometimes in larger cities, the postmasters are a bit elusive so
you may want to call or even visit your post office in person.

Beachcomber