Mortgage agreements sometimes forbid the carrying on of a business in a home. This is very often the case if the mortgage loan has been received from a Government agency. If you live in rented accommodation, the landlord's permission must be obtained. Some home-business owners never bother to apply for zoning permission and carry on business without it. Some get away with it for a long time but they are always vulnerable to having their businesses closed down at short notice.
Some professional organisations impose restrictions on practising from home.
Special permission must be obtained from the professional organisation. Often they impose conditions such as having a separate entrance for clients. The professional organisations for accountants and estate agents are examples. It would be advisable to have a separate entrance for clients if you can manage it. This may involve structural alterations.