There is one aspect I would take into consideration.
It all depends on what you want to do with the server. If you are planing to have something small like a local area network, just quickly eclipse/batch the latest SVN + mysql + whatever else is needed and you are all set for a for a L2 Single player mode :).
If you are thinking of something bigger in the idea of making a profit, L2OFF is defentelty an issue. Why ? the bigger the server gets the more noticeable and exposed you become. Running the L2off code on a private machine is definetly illegal.
Until a better option comes out, you have to stick to the L2J, constantly checking their official devs forum and at least one test server where you can first check the so called "patches"m latest releases and stuff, there`s a high chance a later release is worse than the previous one, same with the bugs. Eventually might cause a big lose on a community level.
It requires a lot of knowledge if you wanna go hardcore in the Java engine, some PHP querring for the DP, HTML for the traders and python for the quest, also XML for the mammon. You will realize at some point that many things are bugged, not working or needs mods to work as it should. The knowledge in the background would HELP a lot.
Machine: You will need a pretty strong one. Yes is a good a idea get a cheap solution for a server, and if things are going well you can always update ram cpu hdd. Just make sure before renting a dedicated, the upgrade option is available and check the prices. Many times, to get a base server is cheap, but upgrading it will cost a fortune. Funny marketing trick.
IF you are planning to run a L2J, take like one or 2 months to familiarize with the whole system if you are new to this, compile the pack on a test machine invite a few friends and see how it woks. If all good, you have the time and the money, after that you can go about purchasing a dedicated srvr and go live.
Hope this is pretty useful insight about L2Jing.
Best regards,
Bogdan.
PS: I speak out of my own experience as a L2J Private server dev so you don`t have to take it for granted.