If you are talking about owning your own masternode : you will need 1000 Dash and you will need to rent a server somewhere, put Linux OS on it and install and update Dash software.
Server costs are about $10 per month.

Link : https://www.dash.org/forum/threads/taos-masternode-setup-guide-for-dummies-updated-for-12-1.2680/

Below link will provide a breakdown of the costs, excluding the server costs :

Link : https://m1.dash-news.de/dashtv/#curr=USD&value=1000



The 1000 Dash can be bought here : https://docs.dash.org/en/latest/introduction/how-to-buy.html

You can also join other people into setting up a shared masternode (you then dont need to have the full 1000 dash and server maintenance will be done by the operator)

Link : https://docs.dash.org/en/latest/masternodes/hosting.html

masternode.me & Splawik's Hosting Services are shared hosting services that you can look into. These are not trustless solutions by itself, but the services are run by community members with
an excellent reputation. Each service will have its own costs and ROI, so compare then both before making a decision.