In order to reduce the overall application expenses and time to market, SaaS (Software as a Service) providers tend to outsource several parts of their IT resources to other services providers. Such outsourcing helps SaaS providers in reducing costs and concentrating on their core competences: software domain expertises, business-processes modeling, implementation technologies and frameworks etc. However, when a SaaS provider offers a single application instance for multiple customers following the multi-tenant model, these customers (or tenants) requirements may differ, generating an important variability management concern. We believe that variability management should also be outsourced and considered as a service. The novelty of our work is to introduce the new concept of Variability as a Service (VaaS) model. It induces the appearance of VaaS providers. The objective is to relieve the SaaS providers looking forward to adopt such attractive multi-tenant solution, from developing a completely new and expensive variability solution beforehand. We present in this paper the first stage of our work: the VaaS meta-model and the VariaS component.