Your going to get worries with most vehicles unfortunately. That's the gamble. I've a client who bought an l322 for £7500. 3.6ltr v8 diesel version and it broke down the same day with powerless issues and 37 faults in the memory. Most historic and some intermittent but three main issues that were cutting the power at speed on the motorway... Scary stuff but reality and most cars will behave the same in that scenario.
If it's older car, stuff will fail and you will have to repair it.
I think should find the best with the most history and get a warranty out on it and enjoy it. Whichever your choice is