There are many differnt vacuums out there for inground pools. Make sure you do your research before making your purchase.
For the most part you can buy a vacuum that suctions from the skimmer (debris goes into your filter) or has a dedicated line using a booster pump or you can purchase a robotic vacuum (debris goes into a filter which you clean periodically)
First and foremost you need to purchase from a company who is going to service this product. Many like to save a few $$ by buying online however buyer beware when it comes time to service. Most pool companies will not service a vacuum that they have not sold.
With vinyl lined pools you may need to purchase a drain cover if you are considering a robotic vacuum all vinyl lined pools have a main drain.
We would be happy to chat with you about some of the makes/models/styles available to find one that will fit your needs.