Check NADA if used. Offer 20% below NADA low retail if it's worth it to you. Then negotiate a price that is worth it to you. Hire a RV inspector if you are not familiar what to look for before you sign anything. Do not get emotionally attached and be ready to walk if you can't get a price that you want. Good luck.
Jerry
Chief USN Retired
2003 Beaver Patriot Thunder C-12 505HP
2004 Dodge Ram 1500 4X4