We're building an 18x40 foot vinyl pool in our backyard and we noticed that the estimate we got for a Helix pool slide is $9,000 through our pool builder but we can buy this same slide online for $5,000 from various pool websites. This is our first rodeo and we don't want to do it wrong, but are we better off having our pool builder plumb for a future slide and then buying the slide separately? Are there any other items that we are better off buying NOT through our pool builder as we build the pool? Thanks in advance, happy for any feedback and input as we go through this process!