$150 will get you a fully integrated user registration system with, if you wish to enable it, email activation for users, profiles (bio), admin control panel, and a protected 'registered users only' area, all with a mysql backend. if your site is suitable, consider the possibility of charging people five or ten dollars to access even deeper features of the site restricted to regular users. i do this myself on a site i run and i make a very good living out of it, and so can you. for a little bit extra, i could code in paypal integration using their excellent IPN system to automate the process (ie, they would make the payment and then their account would instantly, without any work from you, be upgraded or activated.) contact me if you want more details; i can do this job easily and i will do it for you.