Second thing is investing a lot of (mostly) time and money. Running a server requires a little bit of money investment (domain 20$ or so and vps 20$+/monthly) and the rest just falls like free files, web etc. to begin with. You would also need to build a good
TRUSTED team (gms, hgms etc.) because, trust me, you can't run a server alone. Lastly you need a good LEADER, that's up to you to decide.
I created a lot of servers, usually we start good and then somewhere in the middle we get challenged, but if you survive the middle part challenge and maintain good active players afterward, you're up for a long term server
Running an MU Online Server is just like running business, or actually it IS business. You don't always have to make money all the time. But again you need those foundation because once they fall, your server will just shut down.