I agree with what people posted above, avoid hosting a client's site to avoid the admin issues.
Set them up with the site, get paid and your job is over.
With some hosts you can resell the hosting and they take full responsibility for the care of the client. I am thinking of Supanames in the UK. They have an un-branded control panel which is cool. So you pay for the hosting, link your client's dot com domain name to it via nameservers and charge your client whatever you want for the hosting. Job done.