Thinking about buying a 2009 GulfStream Crescendo

[GstreamNewbie]

Greetings all!
I’m totally new to RV Camping but have been interested for a while to learn more and potentially buy a GulfStream to live in for a couple of years and travel around. Now there’s a 2009 GulfStream Crescendo (19 000 miles) for sale in my area which has 2 slide-outs and looks nice on the pictures. Could you help me answer my questions?

1. How many days could you generally expect to go without having to fill up on water / empty the plumbing system?
2. What’s the Rough average cost of parking it at a campsite with facilities (per day?)
3. If you want to park it in your garden for some months and live there, what do you need to install to empty plumbing, fill up water, etc? (Cost?)
4. Could a 2009 with 19 000 miles be considered in ”good condition” Or more ”average”?
5. What potential expensive problems can come up? (Generator failure, engine etc)
6. Do you need to go to specialty workshops in case anything breaks?
7. What annual depreciation should I expect on an RV such as this? Are they hard to sell?