Hi Neil,
Welcome to the forum.
Prices of properties like this vary depending on the area, the size of house, size of plot, condition etc. You could pay 250K for one or you could pay 350-400K.
There are certainly bargains now compared to 2 years or more ago. Prices seem to have stopped falling but there are still some which the owners will take lower offers on if they are desperate to sell.
A pool is only essential when it comes to rentals but for full time living many people now say they would never have a pool again as you are maintaining them for 12 months of the year to probably use them for only 4 months.
If you are not living full t ime you will need a pool maintenance guy ang with chemicals, electricity and paying someone to look after it it will cost you about 100euros per month to run.
The company who installed our pool tell us it is not cost effective to shut them down. They have nightmares with pools that have been shut down for the winter trying to get them right again. You just need to reduce the time on the pumps for the winter months.
For average rental charges I would suggest you look at some rental sites to get an idea of what people charge.
Kind regards
Veronica