I would recommend running mares and geldings separate. You can have larger groups of horses, the herds are more low key, I've never had a horse injury out in the pasture, less buddy sour horses... There is no down side. You might loose a potential boarder "they're always been together.... they luuuv each other...." you don't want those ones anyway. I do not grain the herd. Too dangerous. I do provide salt and a loose mineral/vitamin blend. I do have 12 x12 panel pens up in the loafing shed area that horses can be grained in but it's up to the owner to provide the feed. Hay is provided as part of the board fee. Some places will keep track of how many days hay is provided and charge for each day. Too much work for me. Also helps protect the pastures by being in control of the hay. You need an area where you can lock the horses up off of the pastures in bad rains, if they're overgrazed... I have a common area where the sheds, pens, hay feeders and water are that the pastures connect to (2 pastures per group).
Boarders who want pasture board tend to be less demanding but they still want somewhere to store their stuff, a roundpen or arena even if you're catering to trail riders, trailer parking (you can charge extra for that), a shed, running water (heated tanks in the winter if applicable). I would never have a community tack room. Build individual tack boxes that they can lock up. Only allow them one box per horse and all their stuff must fit in there. That's one reason people love having horse trailers just to store all their extra tack and feed. If you don't grain, than you need to have somewhere for them to store their feed. No garbage cans! They take up too much room and are just an eyesore. If your tack boxes are big enough just make them keep it in there. I've seen nice stackable plastic bins (like big dog food bins) that can hold 100# of feed. They're probably $100 each but well worth it just to reduce clutter.
Other things to think of: Where are you going to store your hay? You need a quarentine area (stall or pen) both for new horses and injury. It's also nice to have if you need to keep a horse up for the vet or farrier. Is zoning a concern? What about neighbors? Manure disposal? Do you have enough land to just spread it or will you have to stockpile it? Will you need to be able to mow pastures (tractor, bush hog) Electricity? Winter blankets yes/no place to store them on warm days, on/off... The more things you can think of and have a game plan before the situation comes up with a boarder, the easier it will be.