Metal detecting is a popular hobby in England, but can you make money from it? Well, for a start, many old and valuable coins and artifacts are found in England every year, but so is a lot of "junk" (although, so called "junk" can be valuable in itself i.e. copper and aluminum etc., but you'll need to find a lot of it!). It takes a lot of hard work and perseverance, but there is also an element of luck. Before you can even contemplate making money from metal detecting, you need a metal detector. These can range from approximately £60 to £1000, then you need a spade etc. So, as you can see, you need to start spending from the start. Then, you'll need to find somewhere to metal detect eg. a park or farmland (but you'll have to ask permission from the "owner" first!).
Some old coins and artifacts found on farmland can be sold in England, once they've been reported and recorded, and some are "bought" by "museums" (this is a complex area, so please read about this elsewhere on official United Kingdom Government run websites). Occasionally, major hoards etc. are found, and these can be worth lots of money, but generally, after a day's metal detecting, you'll come home with items worth relatively little. You will hopefully find old silver coins and artifacts etc., but after you've taken off your travel costs, there is the possibility you'll have lost money, not made it.
To learn more about metal detecting in England, please contact the National Council for Metal Detecting. You may also wish to join a local metal detecting club. There are different laws about metal detecting in other countries, so you should seek further advice. Searching for old coins etc. can be an enjoyable hobby. Your most popular finds may be buttons, old copper coins, scrap etc., but hopefully you will make some "good finds" as well.
In summary, can you make money by metal detecting?......well unless, you're very lucky, or don't have lots of traveling costs, and you live close to good sites, I wouldn't start considering it as a career option!