Another amazing trip and equally well-done TR - thanks! We also love taking family trips in the US and visiting national parks, so I especially enjoy gleaning travel ideas from your TRs. This summer we were in northern MN and WI among other places and got some great ideas from your TR. Unfortunately Isle Royale was closed unless you wanted to pay $300pp to fly in, and houseboats in Voyageurs were all booked up, but we still had a great time.
Even though we've been to most of the places in this TR, we've always wanted to try an RV but have found the logistics daunting (it also helps that we have tons of hotel points so almost never pay for lodging), so I'd love some pointers about how to feel secure enough to go ahead with it. Specifically:
Are there any websites or generally good strategies to use to find good deals on RVs, whether 1-way or just cheap rates?
Are there specific RV rental companies that are more reliable, and any to avoid?
Are there any that include unlimited miles as is standard with car rentals?
In hindsight, were there any red flags you missed or questions you wish you had asked to avoid getting an RV Poopypants? 
Any tips about how to find good places to stay each night?
Did you have prior RV experience, and any advice about how to handle unique RV issues like emptying tanks, leveling, etc., to ensure a successful first experience?
1. I would check with each RV rental company to see if they have any specials. Here is a partial list:
El Monte 1-way specials
https://www.elmonterv.com/rv-rental/cool-deal-detail/ONE-WAY-SPECIAL/Great Alaskan Holidays
https://www.greatalaskanholidays.com/alaska-rv-rentals/specials/Cruise America
https://www.cruiseamerica.com/Apollo RV
https://www.apollorv.com/reloc.aspxRoad Bear RV
http://www.roadbearrv.com/en/rental-dealshttp://www.roadbearrv.com/en/rental-deals/one-way-specialshttps://www.imoova.com/https://www.transfercarus.com/2. We have rented from El Monte, Apollo and Great Alaskan, as best as I can recall. I do not know if there are any to avoid. We have always had some issues with the rentals but I wouldn't characterize the issues we had as a reason to avoid that company in the future.
@Something Fishy once mentioned reading negative things about Apollo but we did not have any issues when renting from them and, at the time, they were one of the cheapest.
3. I think there are some that do include unlimited miles for an added fee, but you would have to check with each rental company. Generally, it is not an option.
4. No red flags that I can specifically point out. All I can say is that I have learned to check all of the major systems of the RV before you take off. Make sure the AC, generator and refrigerator work. Check to see that the outlets work. Make sure the shower and sink work. Turn on the stove and ovens. It pays to spend a few extra minutes before you leave to make sure everything works rather than realizing later on and having to call the RV company and try to diagnose the problem. With this particular 1 way rental, the RV was definitely beat up a lot more than any other rental we had in the past - but then again it was $75 a night. Other 1-way rentals can be brand spanking new RVs that need to be relocated from the factory to the rental company - so you can really luck out there.
5. We like KOA campgrounds as they are a chain and are fairly consistent throughout. We have also found other non chain campgrounds that we liked very much. I'd suggest doing some research about the locations you want to visit. National parks have some really nice campgrounds but those are often without any hookups. You can also camp on BLM land for free but again, no hookups. Info can be found here:
https://www.blm.gov/programs/recreation/camping. Another option is to camp at farms, vineyards and breweries by purchasing a membership here:
https://harvesthosts.com/. The cost is $79 or $119 per year. Finally, if you are on the road and want a free place to stay for the night, most Walmarts allow you to stay overnight in the parking lot. This list is by no means exhaustive.
6. We started renting RVs without any prior experience - just jumped right in. The rental company will show you a video before you take off, which will contain a number of useful tips. There are also many videos on YouTube that you can watch, to learn the basics. Emptying tanks is not hard at all. It's not a pleasant job but I don't understand why people make such a big fuss about it. Likewise, leveling isn't a big deal. Most RVs you rent do not have auto leveling. The rental company provides you with one of those bubble levels. Once you know which side needs to be adjusted, you drive the RV onto one of those small ramps that you are provided with. I am sure it will be a little daunting your first time out, but once you get the hang of it everything will be fine and you will have a great time.
I hope I answered all of your questions. If I missed anything, please let me know.
