I too rent a space in a hair salon.
I pay a flat rate of £20 per day. Just now I only do Sat's as I got a f/time office job & work mobile at nite.
I would advise you to look out for the following;
1/ if you are gonna be actually in the salon - how far away will the hairdressers be? - you done want their hairspray & stuff contaminating all your products! :?
2/ Will you be at a window - NOT a good idea - again think of the impact on your products.
3/ Look at the flooring - is your desk gonna "shudder" every time someone walks past (not good when your trying to create a perfect smile line

- especially if your in the thru route

)
4/If you're not in the salon (ie have a separate room) think about the ventilation (especially if you use L&P) :ack:
5/Cont from last point - if you're not "out there" how are you gonna promote yourself? :goal:
Hope these little points help
Fi XoX