Ok here's a bit of useful information for you, before even considering buying a dedicated server.
3.55 server files, will not run on most dedicated servers. As most dedicated servers, now run Xeon Quad cores with windows 2008 upwards. You would be very lucky to get a single core server, running Server 2003. This would be the same for Dual core servers as well, but be aware if you find a Dual Core provider, that any changes you make to the server IE: modding Core you are liable for any cost to put it right.
King3G however will run from a Quad core on server 2008, but the files are littered with bugs, exploits and cheats.
The only thing you can't do with 3.55, that you can with King3G is add extra items to knew files. With 3.55 you have to remove items out of .wils (which has a limit capacity) in order to add new items. You also can't use someone else client as your own, unless you have modified the client and files.
You can on both, add maps that you create or find. I don't believe you are limited to the amount of map files that can be used or read.
Also you can't open a server, directly using someone elses files. You will get banned from lomcn, the server has to be yours and yours alone. But there is no stopping you from using another server files, to create your own. Just make sure you have that person's permission to use them and don't play of scripts as your own.
As for buying a dedicated server, if you can't afford to keep the server running out of your own pocket for at least 6 month. This means that you are only putting a server online to make money, you've got to be able to sustain your server and not rely on others to do it for you.
Rates: Most Mir 3 players don't like Euro style rates, as it's far to low and they play P/Servers not to have to grind so much. Your average player, prefers between x8 - x32, though there are players who like x128 and above (But with these type of servers, you will be adding content a lot).
You've also got to be prepared to put your own work into the server and work hard on it, otherwise it won't last. Sting3G was up for so long previously because of the content that IdabigA has worked on and added and this is why it's back again under Karl. If you can't put the time and effort into the server, then don't bother bringing one up. It's not easy creating a server and maintaining it and it does require a lot of hard work from you. You've got to be able to put up with a lot of **** from players.