, the short answer is have a blog. Think about questions that your customers frequently ask, and each week write a short blog entry answering that question. Or you could do a write up on a new model of RV or pluses and minuses of different kinds of RVs. You're the expert. Share your knowledge with your site visitors and you'll have great content. Just make sure you don't copy and paste content from other places on your site, or anywhere else. It has to be unique content.
If you don't have time to write unique content every week, I know people who have had success getting high school students to do a very good job for them. A lot of schools have journalism classes or work experience programs, so they'd be very happy to have a local business take on some of their students.