There are a lot of guys on here who have also owned an RX8 so I will let them give a less biased view.
The zed isnt to expensive to run, just make sure you get the cheaper pre 06 tax band, after that its down to your right boot.
Hi and welcome to the forum. You wouldnt be the youngest owner on here so its definately very possible. Check out the FAQ section for a sticky post for new members. There are some good links for buyers in there.
The cars are pretty reliable so apart from a few easily identified issues its down to the normal checks, service history etc.
Due to the scrappage scheme there is now a national shortage of cheap cars, the prices have shot up. Anything clean and in good order will sell very well privately.
I always used to be able to source good little runarounds but there is nothing about now.
As mentioned, Alex is running his setup near 600 bhp from memory, has a hell of a lot of experience and also sources parts so he will be able to give you a lot of pointers.
He also has a roadster as they are faster.
I am sure someone will be advertising a service on TV to cover this one. You may recall why McDonalds have to advertise that their tea and coffee may be hot.