I had an outdoor pool in a past house pre divorce. TBH I loved it and the DC and I got a lot of use out of it. I sold the house easily to a family with three primary school aged children.
We only used it May to October and it was not too expensive to run, probably an extra £100 a month. I used to watch the weather though and turn the heater off if there was a cold or rainy spell as we were all fair weather swimmers.
Learning to look after it yourself is a big money saver, I just paid someone to open it up in May and winterise it in October, the rest I did myself. It is fairly easy to learn and I found it quite relaxing, though you do get a bit obsessed. I can still look at the water in anyone's pool and tell at a glance if it is perfectly balanced. You can use a lot less chlorine in your own pool (unless you have lots of children coming over).
Get a pool cleaning machine which runs off the filter system. It will save you lots of cleaning time.
Have a pool maintenance company check the pool and its system over before you buy, they will do it for free or a low cost.
The only problem is it does ruin you for public pools forever more! Nothing beats getting into a totally still, empty pool to swim.