not sure exact figures but ebay charge around 7.9% and paypal charge around 2%
I increase prices by around 25-35% depending what it is, no use listing a $1000 item and putting $300 on to when your competition has it for $1200, big items its still better to make a little profit than none, in a case like that I am happy to make $20-$30 than lose a sale
depends what country you are from too as to where to sell
Watch your suppliers stock levels, bit embarrassing when you sell something only to find that they are out of stock, I have a few negs becuse of that.
And watch postage costs, if its a large item going from one side of the country to the other, it may cost a fortune, Isold something once for $150 and charged $50 shipping, the shipping cost came to $157, I covered it cause I am an honest seller.