Even if you’re skilled in “complex PHP websites” it’s safer to go with something that’s already built. If you code it yourself you’re very likely to overlook security issues and you’d have to constantly be updating it. It’s worth investing a bit of money in plugins up front (if necessary; you may well do fine with free plugins, just do lots of research up front to see how well supported the plugins are, how many active installs, all that type of plugin vetting you should do in any case) so you don’t have headaches down the road. And if you’re expecting triple-digit income please be sure to find solid managed WP hosting, your own VPS or something similar, so that if things go south you have someone to help immediately.
