Can't speak to the 5th wheel question but for the others:
Will you be traveling all the time or staying put in one area? If so, what area?
1. Check out www.woodalls.com for campgrounds and RV Parks. State and Federal usually have a 2 week stay limit. Privately owned parks usually have monthly rates. After you find some parks, always check them out on www.rvparkreviews.com
2. We spend about $900-$1500 per month on campgrounds. That's an average of $30-$50 per night. That usually includes water, electric and sewer. Sometimes it includes cable. You won't be able to rely on cable or wi-fi. You will need satellite TV and a wi-fi hotspot like Verizon mi-fi. Both are expensive.
If you find parks with monthly rates, most of the time they charge extra for electricity. They usually explain that on their websites and give the amount per KWH they charge. They require a deposit and usually bill monthly for electric. There are also RV Resorts that sell lots. That works if you stay in one place for several months.
For an idea in Florida, check out Williston Crossings RV Resort in Williston FL. It has a nice pool and rents monthly sites. Another problem you will have with campgrounds and RV parks in Florida is that they are geared for snowbirds and cater to older people. When we travel we see lots of families at KOA's and Yogi Jellystone Campgrounds but they do cost more because they have more things for the kiddies. Some in popular areas with lots of amenities could be $100 per night.