you need a huge amount of coins and block them in the wallet, and the wallet has to be online 24/7 and you get a fee, when people are using your node?
care to explain anyone?
If your wallet is on the MN server yes you need to keep it online 24/7 just like the server. If your wallet is on a separate desktop computer then you can remote control the MN from there and turn in on and off as you like without affecting the MN server.
Many like to use a VPS service to run their masternodes. You can get a VPS server for as low as 5-10 US$ per month. I have been fairly happy with Vultr.com.