My actual brewing space, including sink, bench for kettles, room for two ferm chambers (one large, one small), and conical fermenter is about 6 x 12 feet. That doesn't include the grain mill, buckets and such of grain and other ingredients, nor other storage. I'd say that adds....maybe another 40 square feet. So my brewing setup takes up...112 square feet? More or less.
I'd take more room if I had it, but I can brew comfortably within those confines, so I'd suggest that as the minimum. In fact, since you have 700 feet, I'd probably be inclined to set aside 200-250 square feet for that. I'd be thinking about a keezer or other way to keep beer cold and serve through taps on the other side of the wall as part of a bar. Not sure if you want to go there, but if you did, 300 square feet would be more than enough--15 x 20 would be fine.
What would I want if I was spec'ing out a new brew space? I'd have a sink with a sideboard on it, and that sink would NOT be a low stainless or utility sink. I have one that's higher and I wouldn't give it up for anything.
That sink has a normal sink sprayer on it, which I added along with some other plumbing work I had done. It's very easy for me to lay a kettle or a keg on its side and spray it out.
I wish I had a drain right at my brew space; I have one on the other side of the garage and the floor drains to it, but I'd rather have one there. Brewing is messy at times, and while I use a mop to clean things up, spraying it down would be better. Don't know how easy or hard it'll be for you to add a drain if there isn't one. If you had an existing one, maybe you could run a trench drain over to it. I thought about doing that to mine, but it's a long stretch to do that.
You'll want some sort of exhaust system, even if you're doing electric brewing.
Design the space up front for electric. Add capacity for later on if you might need it. And along those lines, having more receptacles is better than having fewer--with several different circuits and breakers. A spot to plug in ferm chamber(s). A spot for a keezer; whatever you think you might, in your wildest dreams, think you could possibly want.
A few pics below showing my brew space. They may give you ideas. The sink is an old metal sink like they used to have in the 30s and 40s. Found it in someone's driveway on junk day and I rescued it. It's terrific. If I were doing something new, I'd put in something similar, i.e., with a shallow bowl and a sideboard on the left side.
Left side of my brew area; the wall next to the green camoflage refrigerator is the left side of the 12' width.
The sink arrangement; this is before I painted the walls behind to clean up the area and make it look more respectable.
I'd be sure, if I were you, to use wall treatments that were bright and cleanable, as best you can.
The sink area after cleaning it all up. One benefit to this arrangement is that I have an RO filter under the sink, fed by a separate line from the sink faucet. I run the water into an Aquatainer to await the next brew day (I fill the kettle with water, then set the RO system to refilling the Aquatainer).
The boil kettle is always on the right; I have it set up with a Steam Slayer so I can drain the effluent right into the sink. It also provides me an easy water source for that Steam Slayer.
Here's a pic that shows some of that:
and a pic showing the Steam Slayer setup. You can see the drain line going back into the sink (the silicone hose). The 1/4" white line from the sink is the RO water filling the Aquatainer. If you look closely you can see the 1/4" translucent line I use to connect to the steam slayer.
A pic showing where the RO system is, pic taken before I added the Steam Slayer stuff:
And the permanent connections, one feeding the RO filter, one feeding the Steam Slayer:
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You asked above what kind of application I used to plan my layout. The application is housed in the six-inch space between my ears. I have limited space to work in for brewing, so everything has been to create the greatest use out of the limited space, and some of this has been borne of necessity, rather than planning.
Whatever you do, plan for additions and upgrades, to electric, plumbing, whatever. Allow yourself the flexibility to add things as you may wish to later on.
Good luck and have fun!