I would distill everything posted so far to mean: get a 64 bit computer with at least 16GB of RAM, RAM is cheap, install software to allow you to run virtual servers, I use virtualbox, create a vm and install the Linux distro of your choice, Centos is a good choice for someone who wants this to translate into a job, and do whatever you are trying to do. You can probably backup to VM's when you are about to try something that might fubar your VM. Then you can recover. Having a large amount of disk space won't hurt. If you really want to compile your own Linux, then you might want to take a look at Arch Linux.