How can i open up a charity shop for a few days?

I was thinking of getting some donations, I have bags of things that are in good condition and that I could sell to charity. I can get LOTS of other donations easily from friends and family. I have noticed charity shops recently don't open for as long, and some are seasonal. The other day a 2 day event was opened in my town centre renting a shop - (a lot of shops are there to rent) Then it closed, and it relied on people to come and donate or buy things for the charity. I would love to do something to raise for Breast Cancer awareness. I am doing a work placement next week and so choose to do it in a charity shop. But I'm not connected with Breast Cancer and I'm unsure to how I am able to open up a charity store. What are the costs and output, how much money would I actually make to charity. Do I come up with my own money to pay the rent? Or do you gain it back with some profit you make, charities are non-profitable businesses but i'm confused to how they expect (if they do) to come up with rent money. I don't mind working and mending the till there as I am currently unemployed at the moment and undergoing placements to get me into work.

Would I receive help from the government?

I have lots of people interested in this and can publicize it well on Facebook with all my followers and if successful will write in to the daily paper about it.

Thanks in advance for any help, I don't know much so no nasty answers please, it's why I'm asking obviously... :-0 It's why it's called Yahoo answers...