
They will ask if they should buy it, so just tell them yes. When a villager walks into Re-Tail just push them over in front of the ore and talk to them.
7,999 bells is the usually the highest price that you can sell them for where it is guaranteed that a villager will buy it.
You can sell the ore at Re-Tail or you can put them up for sell on the flea market spaces at Re-Tail. Some people dig holes around them and the rock to prevent recoil, as hitting the rock pushes you away a little. You need to keep hitting it in succession. You will see an ore which can be sold within the price range of 2,000 bells to 4,000 bells. Hit the new rock with your shovel, and it will blast open. Memorize the rocks that your town started with, because the ore rock will be one that you haven't seen before. Once you find the money rock, hit it multiple times and money should come out! The money rock will change every day. Get your hands on a shovel and look for rocks. Tropical or palm fruit (bananas, coconuts, mangos, durians, lychees and lemons) is worth 250 bells each. Foreign fruit is worth 500 bells each or 3,000 bells if it's perfect. Your native fruit (the first fruit grown in your town, either apples, cherries, pears, peaches or oranges) is worth 100 bells each or 600 bells if it's perfect. Coconut and banana trees are grown on the beach, all the others are grown on the grass. You can plant your fruit to grow more trees. Pearl oysters are worth 1,200 bells each. Scallop shells are worth 600 bells each.
Giants clams and oyster shells are both worth 450 bells each.
Sea snail shells are worth 90 bells each. Seashells can be found on your beach or on the island. Catching rare bugs and fish can get you thousands easily. The prices range from 200-500 bells for tools. Selling them at Re-Tail will get you money fast! Try to also get your hands on tools from Timmy and Tommy Nook.