Since you're asking for "bids" and have a set low end in mind, that would make this an auction, I believe. There are a few rules in place for these, so please update the items in bold.
Auctions must be conducted under the following guidelines.
If you are selling:
1. If you have a reserve, start the bidding at your reserved price.
2. Clearly post an end date and time expressed in GMT.
3. State accepted payment methods.
4. If an auction is not exclusive to WHT, you must display the URL(s) within the thread.
5. End the auction at the end date and time you stated. Or when the "Buy It Now" price is reached, if you listed one.
6. Transfer ownership to the winner.
If you are buying:
1. You are responsible for the bids you place. Bid only if you plan to buy. 2. Publicly post your bid
3. If you win an auction, pay the seller.