I'm pretty sure your example there is exactly what mining is, just with the added functionality of actually "handling" new transactions.
if I think the miner needs a lot of money to use to buy mining equipment, mining is like an investment but not the same and not willing to buy the tools too
not really!
with lots of different altcoins with different levels of difficulty and all kinds of algorithems you can always find something to mine with the computer that you already have. if you are a gamer then you already have a strong GPU capable of producing a decent hashrate. so there is no additional "investment" involved.