Open-source software solution for providing services

[Bobby DogFight]

Does anyone know of an open-source software solution for providing services, for example, accounting, legal, plumbing, electrical, gardening (anything where services are provided, an invoice is created and payment is made after the provision of the services) - as opposed to a shopping cart solution? I'd be grateful to be headed in the right direction.

[jassmee]

open -source software in the net has various service that is related in open source...