Since Masternodes fulfill special functions for a cryptocurrency network but do cost money and effort to operate, they are incentivized by gaining a share of the block rewards in their respective cryptocurrency. The yield varies primarily according to the masternode count and each coin might have different payout periods. A few coins pay out daily; others pay out several times a day.
Masternodes are different to normal full nodes, because they perform several other functions apart from just keeping the full blockchain and relaying blocks/transactions as a full node does in Bitcoin/Litecoin.
Some of the special functions that these nodes perform are:
Increasing privacy of transactions
Doing instant transactions
Participating in governance and voting
Enable budgeting and treasury system in cryptos
