How do deductions work with regards to selling on online stores

Im not sure if I'm going to ask these questions the correct way but here goes.

 

I sell a lot of things on ebay.  Things that I purchase at thrift shops, garage and estate sales.  So, I typically sell them for more than I paid.

 

Q1. The receipts from the thrift stores do not say what the item is, only what department it might be from and the amount.  Will this cause a problem when filing taxes?  Example:  I paid $5 for a vase.  The receipt only says home decor $5. 

 

Q2.  Do I have to itemize every single item I've sold or just do lump sum profit and expenses?  How do deductions work when filing taxes?  I sell an item on ebay for $30 plus S&H. I only paid $5 for the item.  The customer pays $38 ($30 for item)/ $5 for S&H/ $3 for taxes).  Ebay takes their $4 fee and the $3 for taxes. I pay $5 to ship.

 

Q3.  What happens to the sales tax that ebay takes from each sell?

 

Q4. On items that I've purchased this year and plan to resale, but do not actually sell them until next year... do I write off that item in my deductions this year or wait until next year when I actually sell it and make a profit from it?

 

THank You!