Hi Koto and welcome to the node provider community.
How to become a node provider in practice?
You need to wait until the NNS frontend provides a way to register as a node provider. This is expected for end of Q2 2022. Once your proposal is accepted by the community you can create a proposal for a new data center record or choose one that is already in the registry. Once both, the node provider and data center record, are in the registry you can set up and deploy your nodes.
I must lease server in cloud or opposite, I must buy computer for my own and use it in data center. What is cost?
IC nodes are running on professional data center infrastructure. Cloud instances can’t be used for running an IC node. Also by end of Q2 2022 we want to present the new node hardware together with some hardware manufacturers. The costs aren’t clear yet. The last node types were about 10K$. I personally expect the new nodes being in a similar price class as we aren’t reducing the specification. But there is a risk that current issues with global supply chains could even increase the cost per node.
How much ICP constant in fiat I can get for this node. If after years server will removed from neural net, I can use it for my own as my private computer or sold it?
Details about the current node remuneration you can find in this forum post.
The nodes that you onboarded will get rewards once they were added to a subnet. The life cycle of a certain node type isn’t meant to be limited. The IC allows single nodes to die without any impact on the services running in that subnet. As long as the IC has enough nodes of a certain node type to create a subnet these node types will be used and get rewards. The sustainable usage of resources is important to the IC and differentiates again the IC from classic cloud computing. That said the efficiency of server hardware is constantly improving and rewards will need to decrease the more new, more performant types are introduced. Failing hardware will also cause penalties which again can reduce the rewards. This together could lead to node providers deciding to replace their hardware and do whatever they want with the old hardware.