It sounds like what you are needing is more of a donor management system which is like a crm for non profits. They provide membership levels and can process rec

It sounds like what you are needing is more of a donor management system which is like a crm for non profits. They provide membership levels and can process recurring donations and some provide donor login. I work at Kindful.com and we provide these services, but there are many others, so do some research and see what is the best fit for your client.