to my knowledge it should technically be possible because a master node is simply a full node that is responsible for verification of the transactions, ensuring the integrity of the blockchain, and building the blockchain, ... and getting paid for the "work" they do.
but so far nobody has been able to come up with a design that both ensures the decentralization and makes it fraud proof. so they have to add some level of centralization and enforce the node owner to make a large investment in that coin and lock the funds up too.

BTW you are asking the right questions.