You are basing your question on a faulty premise—that even the most advanced client-management software system will somehow make up for the failings of the employee you decided to hire right off the street, with a minimum of screening.
As anyone at NASA can tell you, a sophisticated computer system is no match for a poorly trained employee, who in the best case will be unable to interpret or manipulate the data that the system spits out, and in the worst case will succeed in pressing the wrong button and erasing all the information you've stored about prospective and existing clients. (One day scientists may develop truly self-aware software that resists the determined efforts of human beings to foul things up, but we're not anywhere near to that ideal yet!)
The fact is that even the most “user-friendly” software systems require a certain amount of training on the part of the employees that use them—and if you hire just any administrative assistant, especially one who is not familiar with how computers work, you will just be asking for trouble. Look at it this way: as good as your software is at keeping tabs on prospective clients, emailing them regular newsletters, and automatically updating their contact information, somewhere down the line that person will want to hear from a real, live representative of your firm. If you happen to be in court that day, or tied up in other business, you'll have no choice but to delegate that task to your employee—and if she's not properly trained in customer service, you can kiss that prospective client goodbye.