So we are looking at a used XC 70. Deciding between one between 2004 and 2007, or the newer models between 2008 and 2014. Newer is probably not in our price range. Of those years, are there any to avoid? We found a nice 2009 T6 that looks like a reasonable price. $8500 for a 94,000 mile car. In good shape. I don’t know anything about that year, though. Also found a 2004 XC70 with 131,000 miles that appears to be in good shape for about $3100. I know they are very different cars, but what I’m looking for is to avoid expensive repairs. Suggestions? Thank you.

Neither is infallible, check them out and buy the one you like. Or buy from the most trustworthy seller the car in the best condition (showing the least abuse) with the best service history.

A 2009 T6 whose owner has skipped oil changes will likely be more headaches than a 2004 whose owner has fastidiously maintained it.

Not to put another fly in the ointment but wasn't 2004 the last year of the AW55-50 "B4 Servo" transmission issues in P2 Volvos?

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XC60 / Odyssey

Don’t know about the 2009’s, but a friend has a 2011 XC T6. She has had no problems with it so far but it only has about 40k on it. That is a terrific engine. Fast, torquey and smooth. Downside (for me anyway) is it is a heavy tank and not as anywhere as nimble as the 850’s and earlier V70’s.
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Will I buy another Volvo??? We'll see....

Go for the 2009, the 6 cylinder has a timing chain. It will need a coolant flush after 10 years, along with PS and PB flush. Just normal maintenance. Lower the price if there is no maintenance history.
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Keeping it running is better than buying new

I have 08 XC70 6 Cyl. Does that have timing chain?

Yes.
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Keeping it running is better than buying new