Develop a marketing look-alike profile for prospective customers
The problem is that you only have positive instances (businesses who have become a customer) but no negative instances (businesses who haven't become a customer).  This prevents use of supervised learning.  You could try unsupervised learning -- e.g., a one-class classifier -- but I don't expect it to be particularly effective.

If you had data on businesses who you tried approaching, but ultimately did not become a customer of yours, then you could try applying supervised learning.