I want to build a "she -shed " but I don't really know where to start

How do you intend to keep out any condensation? You may ruin your sewing machine,

You want to install insulation and some wall coverage to keep out the heat and cold. Lowe's sells window units that act as heaters and air conditioning . You'll also need comfortable seating so I'd start scouring thrift stores , Craigslist , FB market , etc. for furniture . As for decor , whatever makes you happy and soothes the soul.

Assuming the shed is basic and without interior walls, i would ask your building dept about a permit as you will using electricity out there. If ok, decide where electric outlets are needed and have an electrician install them. You can then insulate and sheetrock. Is there a window? If not, you might want to have one put in. The floor could be stick on vinyl. Paint, furniture and you are ready to go. If the shed is large enough, perhaps yu could also put a screen door on...maybe have it as a slider?! If you make your "she-shed", please post pics of it! Good luck...you can do it!

Take a look at this Pinterest entry for she-sheds, Kris:

https://www.pinterest.com/trailer_trish/she-sheds/?lp=true

Click on any button at the top of the page to get to the pins you want (ideas, plans, DIY, budget, etc).

There are tons of gorgeous she sheds on Hometalk that can help you get a sense of where to begin- http://www.hometalk.com/search/posts?filter=she%20shed

I can't wait to see yours! keep us posted!