There are a number of posibilities. Before you do anything else try giggling the shift lever as you turn the key to start. There is a safety interlock swith that will only allow the car to start in park and if the switch is loose or broken you'll turn the key and hear nothing. The fix, a new switch, is not an expensive repair.

Since you are hearing nothing when you turn the key it could also be a bad starter relay. These aren't terribly expensive but most mechanics will want to replace the starter at the same time. A decent mechanic can check for this failure by shorting across the relay terminals to see if the starter motor turns over. If you end up installing a rebuilt starter make sure it is a quality rebuild that your mechanic will guarantee. The costs can vary quite a bit but I'd guess a decent independant shop in your neck of the woods could replace it with a rebuilt for about $300.

Check out the neutral safety switch first. My money is on that as being the problem. Good luck.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold