Many platforms allow you to sell NFTs across a variety of blockchains. Two of the more popular marketplaces are OpenSea and Rarible. 

Both allow you to create NFTs on Ethereum without paying fees, using "lazy minting" systems. Lazy minting lets you create an NFT and put it up for sale without writing to the blockchain. When someone buys it, the fees for writing your NFT to the blockchain are added to the sale. Fees are 2.5 %

The catch:

• With OpenSea, you have to initialize your account ($300 to $400 range).
• With Rarible, trying to remove your NFT from sale will cost a fee ($20 to $30).

• Rarible lets you sell NFTs using the Flow blockchain if you sign up for it using the Blocto wallet. However, choosing to use Flow on Rarible will limit you to single edition NFTs. You can't sell them with an auction.
• OpenSea will let you sell using the Polygon blockchain.

When you use non-Ethereum blockchains like Flow or Polygon, people can't use Ethereum to purchase your NFTs without added gas fees. This may put some collectors off.

Wallets are applications you use to store your cryptocurrencies and any NFTs you end up minting or buying. Use a wallet that is compatible with the blockchain you're using.

• MetaMask's wallet is widely supported by Ethereum-based applications like OpenSea, Foundation, etc. 
• Coinbase has its own wallet you can use as an extension or an app and is supported by most platforms.

Once you have the browser extension or app installed, click on "create new wallet", then create a username and password. They will give you a "seed phrase", which is 12 random words. Without it, you can't recover your account.

Once you have a wallet set up, connect it with the NFT marketplace you want to use.

• With OpenSea and Rarible, click the create button in the top left which will ask you to connect your wallet. You will be presented with a list of compatible wallets you can choose from.
• If you installed a Metamark or Coinbase extension, a popup will ask you if you want to connect your wallet.

Caution: Think twice if an unknown site asks to connect to your wallet, as many scammers could try to access your funds or NFTs.

1. Click the Create button in the upper right-hand corner.
2. Click the box with an image icon in it to upload the file you'll be selling as an NFT.
3. Give it a title. Add a URL in the External Link field that points to your website or Twitter account. Use the Description field to explain to potential buyers what your NFT is.
4. You can add text that acts as unlockable content, which the buyer of the NFT will be able to see.
5. Select which blockchain you're minting your NFT to.
6. Click the Create button.
7. Click the Sell button and add the amount and other information.
8. Click the "Complete listing" button.

1. You will be asked whether you want to create a single- or a multiple-edition NFT.
2. Next, upload the digital file using the Choose File button. It will eventually end up on the InterPlanetary File System (IPFS),  a decentralised way to store media.
3. Set your selling options - "fixed price", "open for bids", or "timed auction."
4. Add unlockable content (optional).
5. Choose your collection.
6. Decide if you want the Free Minting option. If you turn it off and use Ethereum, you'll have to pay a gas fee.
7. Give your NFT a title and description.
8. Click the Create button, and complete the next series of actions.