First off, good luck in your search, and whatever decision you make I'm sure you'll be satisfied.
My 2 cents on the matter: Heed the advice you've already received on here, and as far as engine failures go, doing your homework and reading what's on LN Engineering and Jake Raby's Flat 6 Innovations websites will be great education for you. Mikefocke and RandallNeighbour also have excellent sites with plenty of pre-purchase advice and wisdom (Randall's site is
www.iwantaporsche.net, something I wish I'd found prior to my purchase, make sure you read it). Anything mechanical is capable of failing, we all know this, but it helps immensely when you know where the trouble spots are, and plenty of people have gone out of their way to provide that info to us all. So long as you know what to look for, what to expect, and take the necessary steps (particularly preventative maintenance) to alleviate or eliminate these trouble spots, you can drive your car without worry.
Whatever you do, don't baby the car when you get it, and don't go around driving it in fear of a failure at any moment. It's honestly worse for the car to baby it and run the engine at low RPMS than better. Keep the RPMs under 4,000 til the car's warmed up, and keep them anywhere over 3,000 after that while you're driving and cruising.
To go along with what was mentioned before about deciding how much you're willing to spend, also ensure that you're able to budget a few thousand dollars a year for any possible repairs. It won't come as such a heavy blow to you when something does need fixing if you do this.