I don't know if you server hosters know this or not, but hosting a Minecraft server actually requires resources.
You really can't host a server and play at the same time on a dual core, even at 3 GHz.
And no, you can't host on DSL speeds either.
You need at least a quad core processor, at least 2.5 GHz maybe, and at least 4GB of RAM, and at least a decent broadband connection if you live in a rural area, or fiber optics in a populated area.
I'm not saying "NO HOSTING PLEASES", I'm just saying, if you don't fulfill those requirements you'll find out shortly that the server will either lag from the start if you have shoddy internet, or will lag with more players/chunks generated eventually.
I sometimes host a Minecraft server (not as much as I used to), and my RAM usage goes as high as 3.5GB out of 4GB. 1.5 GB is normally used by Steam/Chrome/Windows/Skype/etc. Do the math, Java eats up lots of RAM.