In small businesses, people feel that they are in competition with each other but in reality this is not the case.
Good business needs a healthy customer base but customers come and go so you have to work hard to keep the flow going and keep your customer base continuously refilled.
In professional industries it is commonplace that if a customer had further requirements in allied services to your own, you would recommend them to a business associate, even if they did not work in the same company as yourself.
This would also happen vice versa with other associated industry members according to the needs of that customer.
This should also happen more in local communities where you can help generate business for each other by means of recommendation. If you do recommend a customer to somebody else for an allied service, that business will feel just as happy to recommend someone back to you when the need arises so you both get a to enjoy the win, win accomplishment.