That's a how long is a piece of string question. How long is 'forever'? What can you realistically afford? How much are you prepared to trade off purchase price versus maintenance costs? Are you going to do the work yourself or send it to a mechanic? How 'nice' does it need to be?
From my perspective, if it's a second car it would be doing lower mileage and be a 'lesser' vehicle than the main car. In our case, our second car (actually my wife's car) is a small car that is 10 years old and rarely leaves local suburbia. Its job is to be reliable, economical, cheap to maintain and easy to park. Also had to have a 5 star ANCAP rating when new. It does very low km annually.
You need to start with what the vehicle is going to be doing and what you'll need to spend to get something to match. You said local trips plus some longer trips. This sounds more like the role of a main car. If your situation is that you have 2 or more drivers that use the vehicles equally then you probably need to recognise that and step up to a fairly decent car.
If you're not doing the maintenance yourself and you don't want much, if any, downtime then you need to bring your budget a long way up to get something relatively young. Certainly mid teens but likely 20k or more for a car to keep long term. If you underspend on purchase price you can end up paying it out in repairs anyway. Otherwise with a lower budget you will need to accept that it isn't a 'forever car'.