There is no such thing as too much space for a shop. I bought my
2 bdrm house BECAUSE it had a four car detached garage. Ran 220,
water line, sewer line and gas to it. Finished half of the garage - for
a jewelry shop and converted that for stained glass. Took over the
other half for woodworking. Eventually converted the stained glass
space to a a layout/ assembly/finishing space - with ply storage as
well. There are wood racks under the eaves behind the shop. STILL
don't have enough room - and that's with a 5 function combination
machine (table saw with sliding table, shaper, joiner, planer,
horizontal
mortiser) which has a relatively small footprint - with a "mobility kit"
which lets you turn the unit or move it - a little (it's 1100 pounds).

http://web.hypersurf.com/~charlie2/TheShop/ShopMap.html

It's not just the square footage to consider - but "wood alleys"
and human paths. A table saw location that allows you to open a garage
door or shop door on the infeed side will let you rip 4x8 sheets of ply
lengthwise - a LOT of space needed if you can't use "outside" space.

And table top height - if most are at or above table saw table height
they may do double duty as outfeed tables - but don't count on that
since ALL horizontal surface above floor level get occupied fairly
quickly.

Start with 600 - 800 sf or more. More is always better - just like
clamps ; )