When considering a career change or a new business start up PLANNING is essential. Doing these 2 things at the same time might be possible but success will probably have to come as a result of many small steps and not one giant leap. While there are some grant and low interest loan programs that might be applicable to your situation, there is not any funding that I am aware of targeted specifically for agritourism, especially for a startup. Programs for specialty crop marketing, tourism attraction, value-added processing as well as education and demonstration are avialable through various sources. In most cases though, this funding is not for the purposes of purchasing land, equipment or buildings.
In general, I suggest that you start to develop a business plan to thoroughly investigate the potential opportunities of your ideas. In most cases, switching careers cold turkey does not turn out to be the most feasible idea but depending on your access to land, equipment, equity/credit, marketing skills, past experience, etc. you may be in a position to do just that. Without more information it is hard to offer additional suggestions. Please feel free to contact me directly and I will be happy to answer your questions or help you find someone who can.