Hi mog,
We own a week at Vistana Resort, but I am not a tennis player so am not positive of the answers. I am fairly certain that tennis is free as it is a common ammenity paid for by the homeowner's association for all to use (unlike say the mini-golf that has an extra fee).
I have not seen any equipment avialable in the club house, so can only assume that you need to bring your own.
I think the best way to find out is to call the resort in advance. Just ask for the concierge, and I am sure they will offer an answer to your question.
BTW there are 13 courts available, and i have never seen more than 2-3 in use at any time; expect getting court time will be no problem.
I expect that most of the sections have vaulting on the top floor units, although not all have skylights. I have stayed in an upper in Springs, and it has both. Our owner week is in Courts and we have very impressive vaulting (2 story living room), but no skylights. I have heard of other uppers with skylights, but cannot say for sure which sections as I have yet to stay in an upper in all of the sections (but we're trying...)
Remember that most sections (except Cascades and Lakes) don't have elevators. Buildings are only 2-3 stories high, so we don't mind the walk up to get the extra airiness of the vaulted cielings (and no upstairs neighbors), but many find the stairs to be a hindrance to enjoyment.
Vistana Resort is a fantastic location. Hope you enjoy!
