With Check out dives all teh gear you need "should" be included in the course, however I understand that in some locations they insist you purchase Mask, booties and fins?With the dive computers, is that overkill to have for checkout dives?
Owning your own computer isn't essential, you can rent them for a small fee. The disadvantage of course is that you wont' be familiar with that particular model
Buying your own computer, is of course desirable, but you need to weigh up how much you are going to dive vs the outlay. Its a personal choice. If you were divign regularly or determined to buy a full gear set, then yes
Again as others have said, complete your dives, and then start to decide having had the chance to dive various gear and chat to people.
If you are only diving on vacation occasionally , then one needs to weigh up the pros and cons of renting gear each time for a small fee vs the outlay of a full gear set, ongoing maintenance costs and the "hassle of carting about and storage at home.
I of course own all my own gear and I have numerous different rigs, and am not shy about buying a shiny toy. Even though I dive most weeks, if I was being hard nosed about it and putting on my (wife's) accountants hat on, I would be hard pressed to justify the financial cost of ownership and maintenance vs renting.. So in short it always comes down to a personal choice