You also can't use the (free) ESXi if you are going to resell services.
VMware grants you a nonexclusive, non-transferable license, without rights to sublicense, to install or have installed a single instance of the Software and each Licensed Additional Module on a single Server, unless permitted to have multiple instances on a single Server or to have multiple instances on multiple Servers by the payment of applicable license fees (whether such fees are based on a per Processor, a per Virtual Machine, a per user or any other VMware approved licensing model); (ii) use the Software and each Licensed Additional Module solely for information processing and computing purposes, including the hosting of computer application-based services from a Virtual Machine and provision of such services via an internal or external network, provided such services may not consist of services to a third party that provide primarily computing or processing power (such as utility computing or grid computing) or any computer application-based service that is traded, rented, leased or sold on a Virtual Machine basis; and (iii) use and reproduce the VMware Virtual Infrastructure Client Software or VMware WebAccess (in object code form only) for the purposes of installation and operation on an unlimited number of your own internal computers or terminals solely for the purpose of accessing the Server on which the Software is installed.
Look http://www.vmware.com/resources/compatibility/search.php:
ESX support more hardware than ESXi
You also can't use the (free) ESXi if you are going to resell services.
VMware grants you a nonexclusive, non-transferable license, without rights to sublicense, to install or have installed a single instance of the Software and each Licensed Additional Module on a single Server, unless permitted to have multiple instances on a single Server or to have multiple instances on multiple Servers by the payment of applicable license fees (whether such fees are based on a per Processor, a per Virtual Machine, a per user or any other VMware approved licensing model); (ii) use the Software and each Licensed Additional Module solely for information processing and computing purposes, including the hosting of computer application-based services from a Virtual Machine and provision of such services via an internal or external network, provided such services may not consist of services to a third party that provide primarily computing or processing power (such as utility computing or grid computing) or any computer application-based service that is traded, rented, leased or sold on a Virtual Machine basis; and (iii) use and reproduce the VMware Virtual Infrastructure Client Software or VMware WebAccess (in object code form only) for the purposes of installation and operation on an unlimited number of your own internal computers or terminals solely for the purpose of accessing the Server on which the Software is installed.