I found a nice Ibanez S520EX with EMG pickups for roughly $400 (used). I'm really tempted to buy it, but it has no inlays except on the 12th fret. Could this create problems? Or should I be fine?
Guitars always (I think) have the little dots on the side of the neck, so you should have almost no problems. May take a little bit of getting used to not having them on the fretboard if you look there a lot, but it's not that big a deal.
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if you play in a band it may be hard to play in a situation where there is only light coming from in front of you.... just what i have noticed with my S series. you should buy that guitar though
Even if it doesn't have any marks on top of the neck you will get used to it very quickly. The first guitar I played only had 3 dots. 5th fret, 10th fret and the 12th fret.
Why would it create a problem? There are loads of gutars out there which doesn't have fretmarkers.

It all depends how well you know the fretboard as to whethre you need them or not, but when you're stood up playing you probably can't actually see them anyway.

If you do use them, have a look at the side of the neck - a lot of guitars (especially those without the usual inlays) have markers there instead.
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