Bustoff, you're asking all the right questions for someone considering an RV. Keep asking until you have a better understanding of the whole thing. I guarantee you that once you buy (or possibly rent) and RV you will quickly learn a lot of RV related issues.
In regard to batteries: Your RV will will have a wall monitor with indicator lights that tell you the charge level of your battery(s). It will also tell you how much fresh water you have as well as how full your black (toilet) and gray (shower, sinks) tanks are. Your charged battery will run the water pump & lights. Your generator will also charge your battery(s) while boondocking so that you don't have to run the genny very much if you watch your power usage. This knowledge usually comes from experience (and asking questions here, but experience is best).
We've boondocked at Nascar races and never run out of fresh water and that's over 4 HOT days (with a 60 gallon fresh water tank, but did it with a 34 gallon tank over 10 years ago with a small travel trailer). You will learn how to conserve your water in many ways. Long hot showers aren't really necessary - it's clean and not sticky that counts the most.
I would seriously consider renting a Class C unit (or A if you can find one) because that will certainly give you a good idea what it's all about before investing in an RV. You may even change your mind about what type of RV you want. Having a Class A or C will likely require you to tow a "drive around" vehicle unless you plan ahead and have all your food & supplies before settling into your campsite. A scooter or bicycles work well too if things aren't too far away. But camping at a National Park and then wanting to explore will require that you drive the RV and that's not always possible when exploring/parking due to the RV size. This is why many campers opt for either a travel trailer or 5th wheel. For $50K (or less) you can find some excellent tow vehicles and great trailers. Most trailers do not have a generator on board, but you can purchase a small Honda 2000 like I have and keep yourself charged wherever you are.
Like I said, keep asking questions and exploring your ideas to the point where you know what you want. We've explored areas from New England, to the Rockies, from Canada to Florida and we are not done yet.