A bit off topic, but why don't you resell a VPS to your client and manage it for them? There may be some value there for your client since you presumably already know their setup and have a good relationship with them.
I have a reseller account, and plan to keep reseller accounts. I do not have the time or knowledge to manage a server. I would rather let it to someone else. My current host do not offer managed VDPS/VPS accounts. (I wish they would).
I would like to have a VPS/VDS account that would guess me the extra access the reseller account can give, and yet the server be managed and maintain by someone else.
I have checked out vpscolo.com. I may talk to them and my client. Maybe I'll get it for myself, and have them manage it, and i'll just resell a portion to my client.