It would probably be good to list in more detail what kind of site features you need. But anyhow, if you get a site built for you, the developer would normally provide on-going support. (Heck, repeat business is a big part of maintaining a living.) But it’s worth asking the developer to use software that is widely available, such as a well-known CMS, so that if you do have to switch developers, there will be plenty of people able to pick up where the last provider left off. It’s much harder if the developer has his/her own CMS that nobody else is familiar with.
The features are more of less like ESTY or Bonzana which is a ecommerce sites with social features. Allow people to sign up, sell their product and interact with each other.
So you are selling it is better to buy a ready product
Can I check is it difficult to re-engineering software?