The number one thing I would advise you as a hosting company, be sure to have your hosting company site on a different machine than that of any of your clients. At a minimum your hosting company (site, monitoring, billing, support, live chat, etc etc) should be on a VPS at a minimum or preferrable dedicated server(s). Personally, we use 6 different dedicated servers for our hosting company files. ONLY our company uses these servers - no clients ever have access. Billing/Support is separate from any other portion in our network as users must be able to access those areas even if your main page goes offline (for whatever reason).
Your main page should also have a failover of sorts so that if it does go offline, you can be back online at another location quickly (or automaticlaly), and you can then notify and keep your customers informed as to the issues you may be experiencing.
Who to go with? That depends on the budget and the demands that you have for your site. Do you go with a $4.00/month account or a $40/month VPS - I'd go Dedicated and not let your information be potentially compromised or taken offline by actions of a shared user. If you can't afford Dedicated right now, then a VPS is advised.