Insuring an RV will depend on the size of the RV, the value of the RV and how much insurance coverage you want on the RV.
For basic liability coverage you can expect to pay around $400.00 to $500.00 per year to insurance your RV and if you want to have full coverage on your RV and the RV is a band new RV that you must have full coverage on then you might be paying $800.00 to $1,500.00 per year for full coverage RV insurance.
Your driving record can also factor into your RV insurance costs as well so if you have a good driving record then you might pay less for your RV insurance.
I have an RV and it's a used one and for basic liability RV insurance I pay $600.00 pear year and it's bundled with my other auto and home insurance coverage.
You can shop around online and get RV insurance Quotes and it may be cheaper to just bundle the RV insurance with your current insurance coverage through your insurance company you're using for your other insurance needs.