What are the advantage for how run a master node?
Because for what that I have understand, running a master node has the weight of high hard disk space demanding, low time of synchronization, none "monetary" advantage…
I missing some thing?!?
Back in the days, you had to run a full client to spend Bitcoin or a full node to mine. Nodes are beneficial for Bitcoin as it forms the backbone of the blockchain. Without these nodes, there wouldn't be blockchain or Bitcoin. Bitcoin Core is safer than SPV clients for example since they don't trust miner to enforce the network rules. They are essentially trustless clients. Bitcoin nodes are best to be distributed evenly around the world. The general thinking is the more nodes, the better. The nodes would be beneficial towards anyone near you who is downloading the blockchain since the speed would be faster. There are also lots of features.
Like you mentioned, there are some downsides to running one. The required hard disk space is around 40GB+ as of now. If the block size increases in the future, the amount of increment would be much higher than now. The hard disk price is decreasing due to the introduction of SSD and lower production cost. It doesn't cost much to get a new hard disk. Synchronization is reduced significantly with the introduction of heads-first synchronization. This would allow the client to get the blocks simultaneously from various nodes connected thus reducing the time taken to synchronize. But the bottle neck is there if your CPU isn't very powerful. There isn't any incentive to run a node now although there is a program that randomly rewards users
https://getaddr.bitnodes.io/nodes/incentive/. To run a node, you must first run Bitcoin Core and open TCP port 8333. Ensure that you have more than 8 connections. 8 outgoing and 1 or more incoming.
Gavin Andresen has said that the network doesn't need nodes that shuts down frequently or isn't reliable. Network needs high uptime and reliable ones.