S38 or S14 more expensive to maintain?

For $15k to $20k (US) it's possible to buy a very nice E30 M3 or E34 M5. Just curious how these compare with regards to cost to maintain. I'm thinking particularly about the engine, but am aware that there are other
parts that are specific to these cars as opposed to a regular E30 or E34 -- which means extra expense.
The M3 has always been my dream car, but as I get older (and closer to being able to afford one), the M5 is getting more and more appealing.
I would do little in the way of maintenance myself, relying on an independent specialist familar with these engines. The car wouldn't see any track time, and would be a second car.
Thanks.
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The first thing you ought to do is go to the E34 M5 Buyer's Guide and FAQ and read it:
http://bmwe34m5.com/faqs/?theme=1&level=4&question_id_select@8&chapitre_id_selectC&document_id_select=1&level=3&chapitre_id_select !&document_id_select=3
On M cars, the things that are certainly to be expensive are things specific to each car: that is engine ($10-15K+ to replace), trans (expect to pay in the $6-10K range), catalytic converters (yeah aftermarket ones are available, but to do it right, factory ones start at $1500) to name a few.
E34 M5s have self-leveling rear suspensions. Dinan and others offer removal kits. But, if you want to keep it "stock", be prepared to fork out some $$$$.
Otherwise, find the cleanest one you can, check for things like service records, get it checked out by a good independent shop that specializes in these cars, and enjoy!
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