I work an 8-5 job as well and practice as a VA in the evenings and on weekends. It's very hard, but it can be done. My advice to you - if you can earn bonuses at work, do so and try to earn the maximum. That will be extra money towards your VA practice
Also, do a couple of freebies for someone in exhange for referrals. You'll be surprised how quickly your client base will grow!