Starting in Q3 2018, a user can nominate themselves to become a holder of a masternode. Their application which will be processed by the existing masternodes and, if the user is eligible by all criteria, they will be included in the list of approved nodes.
250 nodes will be available at the start and 50 more using an auction mechanism. But in future the number of masternodes could be increased due to the demands of the ecosystem.
Node creation: the user installs the software for managing the masternode, freezes 250k tokens in the masternode address. After that, they become a member of the network and have the opportunity (if the consensus algorithm choses them) to sign the block transaction and get a reward. Node selection is governed by the order nodes were introduced to the list and the algorithm specifies the desired and the maximum time in which blocks should be produced.