For a small network of sites I would recommend either a shared hosting account ($4.95 for 5GB space / 200GB transfer) or a small VPS server at
XenLayer.com. It is always possible to upgrade instantly if you outgrow your plan:
OpenVZ 1.5 @ $14.95
Core: Intel 1.5 GHz
Guaranteed RAM: 1024 MB
Disk Space: 50 GB
Monthly transfer: 1000 GB
IPs: 1 (IPv4), additional IPs available
Control Panel: VePortal and Virtualmin (cPanel/WHM also available)
All our plans are managed, which includes free migration, periodical checkups, security patches, updates and monitoring of your services. Additional IPs are $6.95/mo for 2 packs of 5 IPs in 2 different c-classes, available on our OpenVZ and XEN servers.