A server has 3 main components - the http service, ftp and pop3.

In addition to PHP you have the following running - apache, mysql, virus scanning, anti-spam software, web statistics, dns server, logs, log rotation, mail queue, a webmail service etc. etc. etc.

All of them use CPU resources - so if you think that 256 Mbs of RAM is sufficient to run a VPS then good luck - you're going to need it.

I suggest you only get a fully managed VPS.

Vger