I can't speak to running a mailing list but guaranteeing delivery to everyone is already a hard task with just one user. Primary difficulty will be getting an IP in a "clean" subnet - the IP that comes with a cheapo VPS will have random neighbors that you can't control and who might get the whole /24 onto blacklists again and again. If you are ok with writing off e.g. Microsoft (hosted Outlook, Hotmail, etc.) or whoever gives you trouble then that makes things easier. This is fine for personal mail depending on what your friends use but with a public service you are going to run into users with problems receiving mail from a random VPS.