Earnings through Tradesy, Poshmark, ThredUp, etc.

If I sell clothing items through Poshmark, Tradesy, ThredUp, etc.

 

1) do I need to complete a 1099

- Is there a certain threshold amount?

- What if I use store credits to purchase goods?

- What if I receive a payout and am payed through Venmo, PayPal, etc?

 

2) if yes, how should I document items sold if they were purchased years ago and I no longer have a record of the purchase.

 

Thanks!