If you want to know what rates you can charge @Jerry500 , you need to carry out market research on what comparable trailers go for in your area and how many days a year you are likely to be able to let it for.
Then you need to put together a profit and loss account with an estimate of your set up and ongoing costs, so you can estimate your income.
STRs are like any other business you need to invest in market research to understand if you are likely to have a successful business model.