Search the internet for companies that assume RV loans. Two examples you will find are dreamrvsforsale.com or internationalmai.com.
Peruse the website you choose to see what RVs are available, and decide which RV suits you best.
Email the owner for more information on the RV. Ask the owner if they are willing to let you assume the loan. Leave your contact information and they will contact you back.
Ask the owner any questions you have about the RV before you sign the contract. The owner must answer every question honestly.
Set up payment arrangements with the owner of the RV through the company.
Sign the contract and make the first payment.
Pick up the RV at the agreed location. Continue to make payments as set up.