Maxine;
I don't want you to come with a misunderstanding. A basic visitors visa is 90 days, the readily available extended stay 6 month visa requires an approved extension at the point of entry. When you arrive at the airport, you will be interviewed. If they determine you do not have set plans to leave at the appointed time you will not be admitted at all, not even for the 90 days. Your return ticket will need to be reserved & paid for. I go through this bs every year!
One time, right on my 50th birthday so I remember it! They held me for 6 hours then rejected me with a list of items (lease, banking info, credit card info, etc) I needed to bring to return. During that time, as I found out later, they randomly called 3 people from my address book regarding my travel plans. One turned out to be my ex husband at work, they taped it, it WAS funny!! I was admitted the next day but they asked how I got the extra money in my bank account so fast. I honestly had received the return of a couple grand of loaned money I never thought I would see in a birthday card waiting at home. I told them, I had been rejected due to insufficient funds as it turns out. It's funny now...sorta'!
You will NOT get a visa extension just because you like it in the USA. You can not even apply for a visa extension without returning to your country of origin & then you can only have been here under a 90 day regular visitor visa as staying for 180 days IS an extension.
I really want you to have a great trip but you need to know that there is no open door or back door policy for immigration to the USA. You are very welcome to come...as a visitor.
You can't even buy & register & insure a RV as a non-resident. I had to have my friend buy my silly little 50cc street legal scooter & then I borrow it because I couldn't register it without a legal ID with an address and it needed a plate. There are a lot of threads on here regarding residency issues & those are state to state.
You might find you need to lease a vehicle if its just to be one visit as it will tie up a significant amount of time to buy & prep a vehicle only to sell it a few months later. You are buying in the high price season in October, and selling in the low season in early March. Vegas itself it a toss of the dice any given day though I think!
Please, do a bit more homework!!