If I have a data center where I can set up the servers and the necessary software, what is the best way to sell the hosting service where I will manage and support the business applications for companies? Basically, I will be the outsourcing company for the applications and off-loading the work from the client companies. I plan to host business applications such as accounting software, HR/Payroll, CRM, ERP, etc.

cold calls and direct contact

i could tell you but then you would owe me a large salary and stock options. i'll need a company car as well.