Asking price is 99000€.
The parc doesn't limit arrival times to just Saturday, it's merely most convenient to rent it out on a weekly basis like that (so my choice). Guests can arrive any day but the parc cleaning crew only works on weekends so if you have guests arriving on a weekday, you'll have to ask them to clean the house themselves if the previous renters left after the previous weekend. Reception is open all days though and in case guests arrive at night there's a keybox with a personal code so guests can get the key. Reception speaks Italian, Dutch, German and English.
There is no property tax, this is included in the "parc costs". Other fees are a tourist tax of 1.5€pp/night but I normally just charge that to guests. There's also a 45€ cleaning fee if you have the cleaning crew clean the house, but I also simply charge it. There's water/electricity usage of course, roughly 500-600€/year.
Yes, you can list it on more sites and get more bookings. I usually have about 7 weeks of the summer booked, with a few weeks in June, September, May and October to reach that 9-10k but if you put more effort into it you can definitely get a lot more bookings. I'm simply too busy with my "regular" work to put much effort into it. There's also travel agencies that guarantee you a certain rent/year like 6-7k and allow you to go for say 3 weeks during the summer and a bunch of weeks during the off season. That's a no-hassle way of making a small profit each year and still be able to enjoy the place yourself.
You should also keep in mind it's best to go there at least once/year to check on things or replace small items like broken glasses/plates. The reception/concierge keeps an eye on everything but they can't check it all.
Edit, found a few on VRBO from the parc:
https://www.vrbo.com/8234040ha?adultsCount=2&arrival=2021-07-03&departure=2021-07-10&unitId=4290173https://www.vrbo.com/10664300ha?adultsCount=2&arrival=2021-07-03&departure=2021-07-10&unitId=5694078https://www.vrbo.com/5083815ha?adultsCount=2&arrival=2021-07-03&departure=2021-07-10&unitId=3636008