Wow--so you want to build your very own baseball "Field of Dreams? Well, unlike the movie, building a baseball field complex is easier said than done! First and foremost, the land on which you build your ballpark has to be zoned for the purpose. This means that the law in the community that governs the land you want to build on allows for such types of recreational use.
There are many, many things to consider. For example, there are issues of parking, lighting, noise and more. The land could also be environmentally sensitive, with wetlands or other concerns nearby. All of these things would be captured in the application to build the baseball field and be reviewed by town experts like zoning officers, engineers and code officials in order to ensure that they are done correctly.
My advice is to start the process by finding a commercial real estate agent to work with. These folks are very specialized salespeople who can help you find the appropriate property and guide you through the long process of getting your baseball field of dreams approved.