I do not plan on having an arena, this will be property for older horses or horses that can no longer be ridden.
I will be feeding the horses, cleaning the stalls and providing turnout for all of the horses. I do not plan on hiring anyone to do the work. Also, all the barns in my area are more expensive than 300.00 per month and most only provide all day turnout for the older horses no riding facility, like mine.

I can’t really give you exact cost estimates because I am not in your area but the cost of property, and you will need atleast 10 acres, is very expensive everywhere. You also need to look at what it will cost to be able to keep up your pastures (fetilizer and seed). If you are planning on having a manure spreader then you have the cost of a tractor and other equipment, I do not recommend a manure pile it attracts to many flies and such. With that you need to decide if you or the boarders are going to clean stalls or hire someone.

I would suggest talking with some barns in your area and asking about their costs, this will give you a better idea of what to do.