Good thing, or bad?
The New York Times profiled a woman who charges $75 an hour for personal training in her apartment's second bedroom. The article reports that there are no formal statistics in New York City on cottage-industry businesses or "number of shingles hanging inside apartments." Some landlords may know of the commercial activity but turn a blind eye because they know this is a way for their tenants to pay for the rent.
However, operating a business out of an apartment can include risks. Depending on the type of business an apartment-based business could violate a lease. It could also run afoul of laws concerning health or city safety codes.
In some cases an apartment-based business can be strictly illegal and could incur strict penalties. A smaller problem might occur if neighbors are annoyed because your business brings in a lot of foot traffic or deliveries. If you're considering operating a small business out of your apartment err on the side of caution and do one that is self-contained.
via The New York Times